 Chapter 38, Part 1 of Principles of Geology this is a LibriVox recording or LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org. Principles of Geology by Charles Lyle, Section 86. Laws which regulate the geographical distribution of species, continued. Geological distribution of animals, buffoon on specific distinctness of quadrupedes of all the new world, doctrine of natural barriers, different regions of indigenous Mamalia, Europe, Africa, India and Indian Archipelago, Australia, North and South America, quadrupedes in islands, range of the Cetacea, dispersion of quadrupedes, their powers of swimming, migratory instincts, drifting of animals on ice flows, on floating islands of drift timber, migrations of Cetacea, habitations of birds, their migrations and facilities of diffusion, distribution of reptiles and their power of dissemination. Geographical distribution of animals, although in speculating on philosophical possibilities set buffoon, the same temperature might have been expected all other circumstances being equal to produce the same beings in different parts of the globe, both in the animal and vegetable kingdoms, yet it is an undoubted fact that when America was discovered, its indigenous quadrupedes were all dissimilar to those previously known in the old world. The elephant, the rhinoceros, the hippopotamus, the camel apart, the camel, the dromedary, the buffalo, the horse, the ass, the lion, the tiger, the apes, the baboons and a number of other mammalia were nowhere to be met with on the new continent. While in the old, the American species of the same great class were nowhere to be seen, the tapir, the llama, the peccary, the jaguar, the koga, the aguti, the paca, the quati and the sloth. This phenomena, although few in number relatively to the whole animate creation, were so striking and so positive in their nature that the great French naturalist sought sight at once of a general law in the geographical distribution of organic beings, namely the limitation of groups of distinct species to regions separated from the rest of the globe by certain natural barriers. It was therefore in a truly philosophical spirit that relying on the clearness of the evidence obtained respecting the larger quadrupedes, he ventured to calling question the identifications announced by some contemporary naturalist of species of animals set to be common to the southern extremities of America and Africa. The migration of quadrupedes from one part of the globe to another observes Dr. Prichard, is prevented by uncongenial climates and the branches of the ocean which intersect continents. Hence, by a reference to the geographical sites of countries, we may divide the earth into a certain number of regions fitted to become the abodes of particular groups of animals. And we shall find on enquiry that each of these provinces, thus conjecturally marked out, is actually inhabited by a distinct nation of quadrupedes. It will be observed that the language of Bafon respecting natural barriers which has since been so popular would be holy without meaning if the geographical distribution of organic beings had not led naturalists to adopt a very generally the doctrine of specific centers, or in other words to believe that each species, whether of plant or animal, originated in a single birthplace. Reject this view and the fact that not a single native quadruped is common to Australia, the Cape of Good Hope and South America, can in no ways be explained by adverting to the wide extent of intervening ocean, or to the sterile deserts, or the great heat or cold of the climates through which each species must have passed before it could migrate from one of those distant regions to another. It might fairly be asked of one who talked of impassable barriers why the same kangaroos, rhinoceros or lamas should not have been created simultaneously in Australia, Africa and South America. The horse, the ox and the dog, although foreign to these countries until introduced by men, are now able to support themselves there in a wild state. And we can scarcely doubt that many of the quadrupeds at present peculiar to Australia, Africa and South America might have continued in like manner to inhabit each of the three continents, had they been indigenous or could they once have got a footing there as new colonists. At the same time, every zoologist will be willing to concede that even if the departure of each species from a single center had not appeared to be part of the plan of nature, the range of species in general must have become limited under the influence of a variety of causes, especially in the class of terrestrial mammalia. Scarcely any one of these could be expected to retain as fair a claim to the title of cosmopolite as man, although even the human race, fitted as it is by its bodily constitution and intellectual resources to spread very wildly over the earth, is far from being strictly cosmopolite. It is excluded both from the arctic and Antarctic circles from many a wide desert and the summits of many mountain chains and lastly from three fourths of the globe covered by water where there are large areas very prolific in animal life, even in the highest order of the vertebrate class. But the habitations of species are as before stated in reference to plants circumscribed by causes different from those which determine their stations and these causes are clearly connected with the time and place of the original creation of each species. As the names and characters of the land quadruplets are much better known to the general reader than those of the other great families of the animal kingdom, I shall select this class to exemplify the zoological provinces into which species are divisible confining myself however to those facts which may help to elucidate some principle or rule apparently followed by the author of nature in regard to that mystery of mysteries, the first peopling of the earth with living beings. First then the European region comprehends Europe, the borders of the Mediterranean and even the north of Africa and extends to Asia beyond the Ural mountains and the Caspian. Although the species are almost all peculiar, the number of characteristic genera is remarkably small. The bear, the fox, the hare, the rabbit, the deer and almost every European form is found equally in several of the other large provinces of Mamalia where the species are distinct, even the mole, Talpa, although confined to the northern parts of the old world ranges eastwards as far as the Himalayas mountains. Secondly the African fauna on the other hand is singularly rich in generic forms not met with in a living state in any other region. The hippopotamus for example of which two very distinct species are known, the giraffe, the chimpanzee, the blue faced baboon, the four fingered monkeys, colubus, many carnivora such as proteles lie to the hyena and a multitude of other forms are exclusively African. A few of the species inhabiting the northern confines of this continent such as the dromedary, lion and jackal are also common to Asia and a much larger number of forms belong equally to the great Asiatic province the species being distinct. The elephant for example of Africa is smaller, has a rounder head and larger ears than the Indian one and has only three instead of four nails on each hind foot. In like manner not one of the three African species of rhinoceros agrees with one of the three Indian kinds. Thirdly the southern region of Africa where that continent extends into the temperate zone constitutes another separate zoological province surrounded as it is on three sides by the ocean and cut off from the countries of milder climate in the northern hemisphere by the intervening torrid zone. In the instances this region contains the same genera which are found in temperate climates to the northward of the line but then the southern are different from the northern species. Thus in the south we find the quagga and the zebra in the north the horse, the ass and the giga tie of Asia. The south of Africa is spread out into fine level plains from the tropic to the cape. In this region says penant besides the horse genus of which five species have been found there are also peculiar species of rhinoceros the hog, the hyrax, among the Pachydermos races and amongst the ruminating, the cape buffalo and a variety of remarkable antelopes as the springbok, the oryx, the nu, the liquefé the pigarga and several others. Fourthly the assemblage of quadrupeds in Madagascar affords a striking illustration of the laws before alluded to as governing the distribution of species in islands. Separated from Africa by the Mozambique channel which is 300 miles wide, Madagascar forms with two or three small islands in its immediate vicinity a zoological province by itself, all the species except one and nearly all the genera being peculiar. The only exception consists of a small insectivorous quadruped centetes found also in the Mauritius to which place it is supposed to have been taken in ships. The most characteristic feature of this remarkable fauna consists in the number of quadrumana of the Lemur family. No less than six genera of these monkeys being exclusively met within this island and a seventh genus of the same called Galago which alone has any foreign representative being found as we might from analogy have anticipated in the nearest main island. Had the species of quadrupeds in Madagascar agreed with those of the contiguous parts of Africa as do those of England with the rest of Europe, the naturalist would have inferred that there had been a land communication since the period of the coming in of the existing quadrupeds. Whereas we may now conclude that the Mozambique channel has constituted an insuperable barrier to the fusion of the continental fauna without of the great island during the whole period that has elapsed since the living species were created. Fifthly another of the great nations of terrestrial mammalia is that of India containing a great variety of peculiar forms such as the sloth bear proculus, the mask deer, moscus, the Nilgau, the gibbon or long armed ape and many others. Sixthly a portion of the islands of the Indian archipelago might perhaps be considered by some geologists as an appendage of the same province in fact we find in the large islands of Java, Samatra and Borneo the same genera for the most part as on the continent of India and some of the same species for example the tapir, tapirus malianus, the rhinoceros of Samatra and Samadurus. Most of the species however are distinct and each island has many and even a few genera peculiar to itself. Between 80 and 90 species are known to inhabit Java and nearly the same number occur in Samatra of these more than half are common to the two islands Borneo which is much less explored has yielded already upwards of 60 species, more than half of which are met with either in Java or Samatra. Of the species inhabiting Samatra are not found in Java Borneo contains the greater portion. Upon the whole if these three large islands were united and a fusion of their respective indigenous mammalia should take place they would present a fauna related to that of continental India and comprising about as many species as we might expect from analogy to discover in an area of equal extent. The Philippine islands are people with another assemblage of species generically related to the great Indian type. Seventhly but the islands of Seleves, Amboyna, Timur and New Guinea constitute a different region of mammalia more ally to the Australian type as having an inter-mixture of marsupial quadrupeds yet showing an affinity also to the Indian in such forms as the deer, serbus, the weasel, Viverra, the pig sus, the macaque monkey, Chercopitecos and others. As we proceed in a south-westerly direction from Seleves to Amboyna and then to New Guinea we find the Indian types diminishing in number and the Australian that these marsupial forms increasing. Thus in New Guinea seven species of parched quadrupeds have been detected and among them two singular three kangaroos yet only one species of the whole seven that is the flying opossum, Petaoris Ariel is common to the Indian archipelago and the mainland of Australia. The greater the zoological affinity therefore between the latter and the New Guinea fauna although it seems in some way connected with geographical proximity is not to be explained simply by the mutual migration of species from one to the other. When Australia was discovered its land quadrupeds belonging almost exclusively to the marsupial or parched tribe such as the kangaroos wombats flying opossums, kangaroo rats and others some feeding on herbs and fruits, other carnivores were so novel in their structure and aspect that they appear to the naturalist almost as strange as if they were the inhabitants of some other planet. We learned from the recent investigations of Mr. Waterhouse that no less than 170 species of marsupial quadrupeds have now been determined and of the whole number all but 32 are exclusively restricted to Australia. Of these 32, 9 belong to the islands in the Indian archipelago before mentioned and the other 23 are all species of opossum inhabiting the tropical parts of South America or a few of them extending into Mexico and California and one the Virginian opossum into the United States. Ninthly, it only remains for me to say something of the mamiferos fauna of the North and South America. It has often been said that where the three continents of Asia, Europe and North America approach very near to each other towards the pole the whole Arctic region forms a zoological and botanical province. The narrow streets which separate the old and new world are frozen over in winter and the distance is further lessened by intervening islands. Many plants and animals of various classes have accordingly spread over all the Arctic lands being sometimes carried in the same manner as the polar bear when it is drifted on floating ice from Greenland to Iceland. But on a close inspection of the Arctic Mamalia it has been found of late years that a very small number of the American species are identical with those of Europe or Asia. The genera are in great part the same or nearly allied but the species are rarely identical and are often very unlike as in the case of the American Badger and that of Europe. Some of the genera of the Arctic America such as the Musk, Ox, Ovibus are quite peculiar and the distinctness of the fauna of the great continents goes on increasing in proportion as we trace them southwards or as they recede further from each other and become more and more separated by the ocean. At length we find that the three groups of tropical Mamalia belonging severally to America, Africa and India have not a single species in common. The predominant influence of climate over all the other causes which limit the range of species in the Mamalia is perhaps nowhere so conspicuously displayed as in North America. The Arctic fauna so admirably described by Sir John Richardson has carefully any species in common with the fauna of the state of New York which is 600 miles further south and comprises about 40 distinct mamifers. If again we travel further south about 600 miles and enter another zone running east and west in South Carolina, Georgia, Alabama and the contiguous states we again meet with a new assemblage of land quadrupeds and these again rivers from the fauna of Texas where frosts are unknown. It will be observed that in this continent there are no great geographical barriers running east and west such as the high snow clad mountains barren deserts or wide arms of the sea capable of checking the free migration of species from north to south. But notwithstanding the distinctness of those zones of indigenous Mamalia there are some species such as the buffalo Bison Americanus racoon Prozion Lothor and the Virginian opossum the Delphi's Virginiana which have a wider habitation ranging almost from Canada to the Gulf of Mexico but they form exceptions to the general rule. The opossum of Texas the Delphi's Carnivora is different from that of Virginia and other species of the same genus inhabit westward of the rocky mountains in California for example where almost all the Mamalia differ from those of the United States. Tenthly the west Indian land the quadrupeds are not numerous but several of them are peculiar. Uneleventhly South America is the most distinct with the exception of Australia of all the provinces in which the Mamalia can be classed geographically. The various genus of monkeys for example belong to the family of Platirini a large natural division of the Quadrumana so named from their widely separated nostrils. They have a peculiar dentition and many of them prehensile tails and are entirely unknown in other quarters of the globe. The sloths and armadillos the true blood sucking bats or vampires filostomide the capivara the largest of the rodents the carnivorous Quatimondi Nassua and the great many other forms are also exclusively characteristic of South America. In Peru and Chile it says humbled the region of the grasses which is at the elevation of from 12,300 to 15,400 feet is inhabited by crowds of Lama, Guanaco and Alpaca. These quadrupeds which here represent the genus Camel of the ancient continent have not extended themselves either to Brazil or to Mexico because during their journey they must necessarily have descended into regions that were too hot for them. In this passage it would be seen that the doctrine of specific centers is tacitly assumed. Quadrupeds in islands Islands remote from continents especially those of small size are either destitute of quadrupeds except such as have been conveyed to them by man or contain species peculiar to them. In the Galapagos Archipelago no indigenous quadrupeds were found except one mouse which is supposed to be distinct from any either to found elsewhere. A peculiar species of fox is indigenous to the Falkland Islands and a rat in New Zealand which last country notwithstanding its magnitude is destitute of other Mamali except bats and these says Dr. Prichard may have made their way along the chain of islands which extend from the shores of New Guinea far into the Southern Pacific. The same author remarks that among the various groups of fertile islands in the Pacific no quadrupeds have been met with except the rat of few bats as above mentioned and the dog and hog which appear to have been conveyed either by the natives from New Guinea. Rats are to be found even on some desert islands whether they may have been conveyed by canoes which have occasionally approached the shore. It is known also that rats occasionally swim in large numbers to considerable distances. Geographical range of the Cetacea It is natural to suppose that the geographical range in the different species of Cetacea should be less correctly ascertained than that of the terrestrial mammals. It is however well known that the whales which are obtained by our fissures in the South Seas are distinct from those of the North and the same dissimilarity has been found in all the other marine animals of the same class so far as they have yet been studied by naturalists. Dispersion of quadrupeds Let us now inquire what facilities the various land quadrupeds are in favor of spreading themselves over the surface of the earth. In the first place, as their numbers multiply, all of them whether they feed on plants or prey on other animals are disposed to scatter themselves gradually over as wide an area as is accessible to them. But before they have extended their migrations over a large space they are usually arrested either by sea or a zone of an uncongenial climate or some lofty and unbroken chain of mountains or attract occupied by a hostile and more powerful species. Their powers of swimming Rivers and narrow frits can seldom interfere with their progress. For the greater part of them swim well and few are without this power when urged by danger and pressing want. Thus amongst beasts of prey the tiger is seen swimming about among the islands and creeks in the delta of the Ganges and the jaguar traverses with ease the largest streams maker. The bear also and the bison cross the current of the Mississippi. The popular error that the common swine cannot escape by swimming when thrown into the water has been contradicted by several curious and well authenticated instances during the floods in Scotland in 1829. One pig only six months old after having been carried down from Garmouth to the bar at the mouth of Spey, a distance of a quarter of a mile, swam four miles eastward to Port Gordon and landed safe. Three others of the same age and litter swam at the same time five miles to the west and landed at Blackhill. In an adult and wild state these animals would doubtless have been more strong and active and might when hard pressed have performed a much longer voyage. Hence islands remote from the continent may obtain inhabitants by casualties which like the late storms in Mauritius may only occur once in many centuries or thousands of years under all the same circumstances. It is obvious that powerful tides, winds and currents may sometimes carry along quadrupeds capable in like manner of preserving themselves for hours in the sea to very considerable distances and in this way perhaps the Tapir Indicus may have become common to Sumatra and the Manleyan Peninsula. To the elephant in particular the power of crossing rivers is essential in a wild state for the quantity of food which a herd of these animals consumes renders it necessary that they should be constantly moving from place to place. The elephant crosses the streaming two ways. If the bed of the river be hard and the water not of too great a depth he forwards it. But when he crosses great rivers such as the Ganges and the Niger the elephant swims deep so deep that the end of his trunk only is out of the water. For it is a matter of indifference to him whether his body be completely immersed provided he can bring the tip of his trunk to the surface so as to breathe the external air. Animals of the dear kind frequently take to the water especially in the rutting season when the stags are seen swimming for several weeks at a time from island to island in search of the dose especially in the Canadian lakes and in some countries where there are islands near the seashore they fearlessly enter the sea and swim to them. In other regions in North America the elk of that country is frequently pursued for great distances through the water. The large herbivorous animals which are gregarious can never remain long in a confined region as they consume so much vegetable food. The immense herds of bison, both Americanos which often in the great valleys of the Mississippi and its tributaries blacken the surface of the prairie lands are continually shifting apart in their rear. It is no exaggeration says Mr. James to assert that in one place on the banks of the plot at least 10,000 bisons burst on our site in an instant. In the morning we again sought the living picture but upon all the plane which last evening was so teeming with noble animals not one remained. Migratory Instincts. Besides the disposition common to the individuals of every species slowly to extend their range in search of food in proportion as their numbers augment, a migratory instinct often develops itself in an extraordinary manner when after an unusually prolific season or upon a sudden scarcity of provisions great multitudes are threatened by famine. It may be useful to enumerate some examples of these migrations because they may put us upon our guard against attributing a high antiquity to a particular species merely because it is diffused over a great space. They show clearly how soon in a state of nature a newly created species might spread itself in every direction from a single point. In very severe winters great numbers of the black bears of America migrate from Canada into the United States but in milder seasons when they have been well fed they remain and hibernate in the north. The reindeer which in Scandinavia can scarcely exist to the south of the 65th parallel means in consequence of the greater coldness of the climate of the 50th degree in Chinese tartary and often rolls into a country of more southern latitude than any part of England. In Lapland and other high latitudes the common squirrels whenever they are compelled by want of provisions to quit their usual abodes migrate in amazing numbers and travel directly forwards allowing neither rocks nor forests nor the broadest waters to turn them from their course Great numbers are often drowned in attempting to pass freeth and rivers. In like manner the small norway rats sometimes pursues its migrations in a straight line across rivers and lakes and penanting forms us that when the rats in Kamchatka become too numerous they gather together in the spring and proceed in great bodies westward swimming over rivers, lakes and arms of the sea many are drowned or destroyed by waterfowl or fish as they have crossed the river Pekinsk at the head of the Gulf of the same name they turn southward and reach the rivers of Judoma and Okotsk by the middle of July a district more than 800 miles distance from their point of departure. The lemmings also a small kind of rat are described as natives of the mountains of Colin in Lapland and once or twice in a quarter of a century they appear in vast numbers advancing along the ground and devouring every green thing innumerable bands march from the Colin through the northern and fin mark to the western ocean which they immediately enter and after swimming about for some time perish. Other bands take their route through Swedish Lapland to the Bothian Gulf where they are drowned in the same manner. They are followed in their journeys by bears wolves and foxes which prey upon them unseasantly they generally move in lines which are about 3 feet from each other and exactly parallel going directly forward through rivers and lakes and when they meet with stacks of hay or corn knowing their way through them instead of passing around. These excursions usually precede a rigorous winter of which the lemmings seem in some way forewarned. Vast troops of Wild S or Onagar of the ancients which inhabit the mountainous deserts of great tartary feed during the summer in the tracks east and north of Lake Arau. In autumn they collect in herds of hundreds and even thousands and direct their course towards Persia to enjoy a worm retreat during winter. Bands of two or three hundred quaggas as species of Wild S are sometimes seen to migrate from the tropical plains of southern Africa to the vicinity of the Malalavine river during their migrations they are followed by lions who slaughter them night by night The migratory swarms of the springbok or Cape Antelope afford another illustration of the rapidity with which a species under certain circumstances may be diffused over a continent When the stagnant pools of the immense deserts south of the Orange River dry up which often happens after intervals of three or four years, myriads of these animals desert the patched soil and pour down like a deluge on the cultivated regions near the Cape The havoc committed by them resembles that of the African locusts and so crowded are the herds that the lion has been seen to walk in the midst of the compressed phalanx with only as much room between him and his victims as the fears of those immediately around could procure by pressing outwards. Dr. Horsfield mentions a singular fact in regard to the geographical distribution of the Medeus melliscepts an animal intermediate between the Polcat and the Badger it inhabits Java and is confined exclusively to those mountains which have elevation of more than 7,000 feet above the level of the ocean. On these it occurs with the same regularity as many plants. The long extended surface of Java abounding with conical points which exceed the elevation affords many places favorable for its resort. On ascending these mountains the traveler scarcely fails to meet with this animal which from its peculiarities is universally known to the inhabitants of these elevated tracts. While also the plains it is a strange to an animal from a foreign country. In my visit to the mountainous districts I uniformly met with it and as far as the information of the natives can be relied on it is found on all the mountains. Now if asked conjecture how the Medeus arrived at the elevated regions of each of these isolated mountains we might say that before the island was peopled by man by whom their numbers are now thinned they have multiplied so as to be forced to collect together and migrate in which case notwithstanding the slowness of their emotions some few would succeed in reaching another mountain some 20 or even perhaps 50 miles distance. For although the climate of the hot intervening plains would be unfavorable to them they might support it for a time and would find their abundance of insects on which they feed volcanic eruptions which at different times have covered the summits of some of these lofty cones with sterile sand and mashes may have occasionally contributed to force on these migrations. End of section 86. Chapter 38 part 2 of Principles of Geology. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer please visit LibriVox.org Chapter 38 Laws which regulate the geographical distribution of species continued. Part 2 Drifting of Animals on Ice Flows The power of the terrestrial mammalia to cross the sea is very limited and it was before stated that the same species is scarcely ever commented districts widely separated by the ocean. If there be some exceptions to this rule they generally admit of explanation for there are natural means whereby some animals may be floated across the water and the sea may in the course of ages wear a wide passage through a neck of land leaving individuals of a species on each side of the new channel. Polar bears are known to have been frequently drifted on the ice from Greenland to Iceland. They can also swim to considerable distances for Captain Perry on the return of his ships to Barrow Straits met with a bear swimming in the water about midway between the shores which were about forty miles apart and where no ice was in sight. Near the east coast of Greenland, observed Scorsby, there have been seen on the ice in such quantities that they were compared to flocks of sheep on a common and they are often found on field ice above two hundred miles from the shore. Wolves in the Arctic region often venture upon the ice near the shore for the purpose of preying upon young seals which they surprise when asleep. When these ice flows get detached the wolves are often carried out to sea and though some may be drifted to islands or continents, the greater part of them perish and have been often heard in this situation howling dreadfully as they die by famine. During the short summer which visits Melville Island various plants push forth their leaves and flowers the moment the snow is ground and form a carpet spangled with the most lively colors. These secluded spots are reached annually by herds of musk oxen and reindeer which travel immense distances over dreary and desolate regions to graze undisturbed on these luxuriant pastures. The reindeer often pass along in the same manner by the chain of these solution islands from Bering Strait to Kamachka subsisting on the moss found in these islands during the passages. But the musk ox notwithstanding its migratory habits and its long journeys over the ice does not exist either in Asia or Greenland. On floating islands of driftwood within the tropics there are no ice flows but as if to compensate for that mode of transportation there are floating islands of matted trees which are often born along through considerable spaces. These are sometimes seen sailing at the distance of 50 or 100 miles from the mouth of the Ganges moving trees standing erect upon them. The Amazon, the Congo and the Orinoco also produce these verdant rafts which are formed in the manner already described when speaking of the great raft of the Achefalia on arm of the Mississippi where a natural bridge of timber 10 miles long and more than 200 yards wide existed for more than 40 years supporting a luxuriant vegetation and rising and sinking with the water which flowed beneath it. On these green aisles of the Mississippi of Zura's Malte Brune young trees take root and the pistia and nanofar display their yellow flowers. Serpents, birds and the Cayman alligator come to repose there and all are sometimes carried to the sea engulfed in its waters. Spicks and marshias relate that during their travels in Brazil they were exposed to great danger while sending the Amazon in a canoe from the vast quantity of driftwood constantly repelled against them by the current and much so that their safety depended on the crew being always on the alert to turn aside the trunks of trees with long poles. The tops alone of some trees appeared above water. Others had their roots attached to them with so much soil that they might be compared to floating aisles. On these, say the travelers, we saw some very singular assemblages of animals pursuing peacefully their uncertain way in strange companionship. On one raft were several grave-looking storks on the side of a party of monkeys who made comical gestures and burst into loud cries on seeing the canoe. On another was seen a number of ducks and divers sitting by a group of squirrels. Next came down upon the stem of a large rotten cedar tree an enormous crocodile by the side of a tiger-cat both animals regarding each other with hostility and mistrust but the soaring and being evidently most at his ease as conscious of his superior strength. Similar green rafts principally composed of canes and brushwood are called chemilotes on the piranha in South America and they are occasionally carried down by inundations bearing on them the tiger, caiman, squirrels, and other quadrupeds which are said to be always terror-stricken on their floating habitation. Though less than four tigers, pumas, were landed in this manner one night in Monteviedo, latitude 35 south to the great alarm of the inhabitants who found them prowling the streets in the morning. In a memoir lately published a naval officer relates that, as he returned from China by the eastern passage, he fell in among the Molakas with several small floating islands of this kind covered with mangrove trees interwoven with underwood. The trees and shrubs retained their verdu receiving nourishment from a stratum of soil which formed a white beach round the margin of each raft where it was exposed to the washing of the waves and the rays of the sun. The occurrence of soil in such situations may easily be explained for all the natural bridges of timber which occasionally connect the islands of the Ganges, Mississippi, and other rivers with their banks are exposed to floods of water densely charged with sediment. Captain W. H. Smith informs me that when cruising in the Cornwallis amidst the Philippine islands he has more than once seen after those dreadful hurricanes called typhoons floating masses of wood with trees growing upon them and ships have sometimes been in eminent peril as often as these islands were mistaken for terror firmer when in fact they were in rapid motion. It is highly interesting to trace, in imagination, the effects of the passage of these rafts from the mouth of a large river to some archipelago such as those in the South Pacific raised from the deep in comparatively modern times by the operations of the volcano in the earthquake and the joint labors of coral animals and Testacea. If a storm arrives and the frail vessel be wrecked still many a bird and insect may succeed in gaining, by flight, some island of the newly formed group while the seeds and berries of herbs and shrubs which fall into the waves may be thrown upon the strand. But if the surface of the deep become and the rafts are carried along by a current or wafted by some slight breath of air fanning the foliage of the green trees it may arrive after a passage of several weeks at the bay of an island into which its plants and animals may be poured out as from an arc and thus a colony of several hundred new species may at once be naturalized. The reader should be reminded that I merely advert to the transportation of these rafts as of an extremely rare and accidental occurrence but it may account in tropical countries for some of the rare exceptions to the general law of the confined range of Memoferis species. Migrations of the Testacea. Many of the Testacea, the whales of the northern seas for example, are found to desert one tract of the sea and to visit another very distant when they are urged by want of food or danger. The seals also retire from the coast of Greenland in July, return again in September and depart again in March to return in June. They proceed in great droves northward directing their course where the sea is most free of ice and are observed to be extremely fat when they set out on this expedition and very lean when they come home again. Species of the Mediterranean, Black Sea, and Caspian identical. Some naturalists have wondered that the sea calves, dolphins, and other marine mammalia of the Mediterranean and Black Sea should be identical with those found in the Caspian and among other fanciful theories they have suggested that they may dive through subterranean conduits and thus pass from one sea into the other but as the occurrence of wolves and other noxious animals on both sides of the British Channel was adduced by Verstegen and Schmarast as one of many arguments to prove that England and France were once united so the correspondence of the aquatic species of the inland seas of Asia with those of the Black Sea tend to confirm the hypothesis for which there are abundance of independent geological data that those seas were connected together by straits at no remote period in the Earth's history. Geographical distribution and migrations of birds. I shall now offer a few observations on some of the other divisions of the animal kingdom. Birds, notwithstanding their great locomotive powers, form no exception to the general rules already laid down, but in this class, as in plants and terrestrial quadrupeds, different groups of species are circumscribed within definite limits. We find, for example, one assemblage in the Brazils, another in the same latitudes in Central Africa, another in India, and a fourth in New Holland. Of 26 different species of land birds found in the Galapagos octrobolego, all, with the exception of one, are distinct from those inhabiting other parts of the globe. And in other octrobolegos, a single island sometimes contains a species found in no other spot on the whole Earth, as exemplified in some of the parrot tribes. In this extensive family, which are with few exceptions inhabitants of tropical regions, the American group has not one in common with the African, nor either of these with the parrots of India. Another illustration is afforded by that minute and beautiful tribe, the hummingbirds. The whole of them are, in the first place, peculiar to the New World. But some species are confined to Mexico, while others exist only in some of the West India islands and have not been found elsewhere in the Western Hemisphere. Yet there are other species of this family which have a vast range, as a trocholus flamathorns, or melasuga kinji, which is found over a space of 2,500 miles on the west coast of South America, from the hot dry country of Lima to the humid forests of Tierra del Fuego. Captain King, during his survey in the years 1826 to 30, found this bird at the Straits of Magellan in the month of May, the depth of winter, sucking the flowers of a large species of fuchsia in the midst of a shower of snow. The ornithology of our own country affords one well-known and striking exemplification of the law of a limited specific range, for the common grouse, tetrascodius, occurs nowhere in the known world except in the British Isles. Some species of the vulture tribe are said to be cosmopolites, and the common wild goose, Ancelesius, Lin, if we may believe some ornithologist, is a general inhabitant of the globe, from Lapland to the Cape of Good Hope, frequent in Arabia, Persia, China and Japan, and in the American continent from Hubsons Bay to South Carolina. An extraordinary range has also been attributed to the Nightingale, which extends from western Europe to Persia, and still further. In a work entitled Specialo Comparatavio by Charles Bonaparte, many species of birds are enumerated as common to Rome and Philadelphia. The greater part of these migratory, but some of them, such as the long-eared owl, Strix Autus, are permanent in both countries. The correspondent of the ornithological fauna of the eastern and western hemispheres increases considerably, as might have been anticipated in high northern latitudes. Their Facilities of Diffusion In parallel zones of the northern and southern hemispheres, a great general correspondence of form is observable, both in the aquatic and terrestrial birds, but there is rarely any specific identity, and this phenomenon is truly remarkable, when we recollect the readiness with which some birds, not gifted with great powers of flight, shift their quarters to different regions, and the facility with which others, possessing great strength of wing, perform their aerial voyage. Some migrate periodically from high latitudes to avoid the cold of winter and the accompaniment of cold, scarcity of insects and vegetable food. Others, it is said, for some particular kinds of nutriment required for rearing their young. For this purpose they often traverse the ocean for thousands of miles and recross it at other periods with equal security. Periodical migrations, no less regular, are mentioned by Humboldt of many American waterfowl, from one part of the tropics to another, in a zone where there is the same temperature throughout the year. immense flights of ducks leave the valley of the Orinoco, when the increasing depths of its waters and the flooding of its shore prevent them from catching fish, insects, and aquatic worms. They then take themselves to the Rio Negro and Amazon, having passed from the eighth and third degrees of north latitude to the first and fourth of south latitude, directing their course south-southeast. In September, when the Orinoco decreases and reenders its channel, these birds return northward. The insectivorous swallows which visit our island would perish during winter, if they did not annually repair to warmer climes. It is supposed that in these aerial excursions the average rapidity of their flight is no less than fifty miles an hour, so that, when aided by the wind, they soon reach warmer latitudes. Spallanzani calculated that the swallow can fly at the rate of ninety-two miles an hour and conceived that the rapidity of the swift might be three times greater. The rate of flight of the Eiderduck, Anas Moltacima, is said to be ninety miles an hour and Bachman says that the hawk, Wild Pigeon, Colombo Magritoria, and several species of wild ducks in North America fly at the rate of forty miles an hour, or nearly a thousand miles in twenty-four hours. When we reflect how easily different species in a great lapse of ages may be each overtaken by gales and hurricanes and abandon themselves to the tempest to be scattered at random throughout various regions of the earth's surface, where the temperature of the atmosphere, the vegetation, and the animal productions might be suited to their wants, we shall be prepared to find some species capriciously distributed and to be sometimes unable to determine the native countries of each. Captain Smith informs me that when engaged in his survey of the Mediterranean he encountered a gale in the Gulf of Lyon at a distance of between twenty and thirty leagues from the coast of France, which bore along many land-birds of various species, some of which are lighted on the ship, while others were thrown with violence against the sails. In this manner islands become tenanted by species of bird inhabiting the nearest mainland. Geographical distribution and dissemination of reptiles A few facts respecting the third-grade class of vertebrated animals will suffice to show that the plant of nature in regard to their location on the globe is perfectly analogous to that already exemplified in other parts of the organic creation, and has probably been determined by similar causes. Habitations of Reptiles The Gavials which inhabit the Ganges differ from the Cayman of America or the Crocodile of the Nile. The monitor of New Holland is specifically distinct from the Indian species, these latter again from the African and all from their co-geners in the New World. So in regard to snakes we find the Boa of America represented by the Python, a different though nearly ally-genus in India. America is the country of the rattlesnake, Africa of the Sarastus, and Asia of the Hooded Snake or Cobra de Capelo. The amphibious Genera Siren and Monopama belong to North America, possessing both lungs and gills, and respiring at pleasure either air or water. The only analogous animal of the Old World is the Proteus Arganius of the Lakes of Lower Canolia, and the Grotto of Ellsberg between Trieste and Vienna. There is a legend that St. Patrick expelled all reptiles from Ireland, and certain it is none of the three species of snakes common in England nor the toad have been observed there by naturalists. They have our common frog and our water-nute, and according to Ray, Quad 264, the Green Lizard, La Tierra Verdes. Migrations of the larger reptiles. The range of the larger reptiles is, in general, quite as limited as that of some orders of the terrestrial mammalia. The great Sarians sometimes cross a considerable tract of water to pass from one river to another, but their motions by land are generally slower than those of quadrupeds. By water, however, they may transport themselves to distant situations more easily. The larger alligator of the Ganges sometimes descends beyond the brackish waters of the delta into the sea, and in such cases it might chance to be drifted away by a current, and survive till it reaches shore at some distance, but such casualties are probably very rare. Turtles migrate roads from one part of the ocean to another during the over-positing season, and they find their way annually to the island of Ascension, from which the nearest land is about 800 miles distance. Dr. Fleming mentions that an individual of the hawks' bill turtle, Terlonia imbrecata, so common in the American seas, has been taken at Papastore, one of the West Settlin Islands, and according to Sybold, the same animal came into Orkney. Another was taken in 1774 in the Severn, according to Turton. Two instances also of the occurrence of the Leatherin tortoise, C. Cordiazia, on the coast of Cornwall in 1756 are mentioned by Borleys. These animals of more southern seas can be considered only as dragglers, attracted to our shores during uncommonly warm seasons by an abundant supply of food, or carried by the Gulfstream, or driven by storms to high latitudes. Some of the smaller reptiles lay their eggs on aquatic plants, and these must often be born rapidly by rivers, and conveyed to distant regions in a manner similar to the dispersion of seas before adverted to. But that the larger Ophidians may be themselves transported across the seas is evident from the following most interesting account of the arrival of one at the island of St. Vincent. It is worthy of being recorded, says Mr. Gilding, that a noble species of the boa constrictor was lately conveyed to us by the currents, squisted round the trunk of a large sound cedar tree, which had probably been washed out of the bank by the floods of some great South American river, while its huge folds hung on the branches as it waited for its prey. The monster was fortunately destroyed after killing a few sheep, and his skeleton now hangs before me in my study, putting me in mind how much reason I might have had to fear in my future rambles through the forests of St. Vincent had this formidable reptile been a pregnant female and escape to a safe retreat. End of Chapter 38 Part 2 Recording by Todd Chapter 39 Part 1 of Principles of Geology This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org Principles of Geology by Charles Lyall Section 88 Chapter 39 Laws Which Regulate the Geographical Distribution of Species Continued Part 1 Geographical Distribution and Migration of Fish of Testatia of Zooofites Distribution of Insects Migratory Instincts of Some Species Certain Types Characterize Particular Countries Their Means of Dissemination Geographical Distribution and Diffusion of Man Speculations as to the Birthplace of the Human Species Progress of Human Population Drifting of Canoes to Vast Distances On the Involuntary Influence of Man in Extending the Range of Many Other Species Geographical Distribution and Migrations of Fish Although we are less acquainted with the Habitations of Marine Animals than with the grouping of the Terrestrial Species before described, yet it is well ascertained that their distribution is governed by the same General Laws. The only Born by Measures Perron and Le Sur to this important fact is remarkably strong. These eminent naturalists, after collecting and describing many thousands of species of marine animals which they brought to Europe from the Southern Hemisphere, insist most emphatically on their distinctness from those north of the Equator. And this remarkably extend to animals of all classes from those of a more simple to those of a more complex organization, from the Sponges and Medusae to the Cetaceae. Among all those which we have been able to examine, say they, with our own eyes or with regard to which it has appeared to us possible to pronounce with certainty, there is not a single animal of the Southern Regions which is not distinguished by essential characters from the analogous species in the Northern Seas. On comparing the freshwater fish of Europe and North America, Sir John Richardson remarks that the only species which is unequivocally common to the two continents is the pike, Esaux Lucius, and it is curious that this fish is unknown to the westward of the Rocky Mountains, the very coast which approaches nearest to the Old Continent. According to the same author, the genera of freshwater fish in China agree closely with those of the Peninsula of India, but the species are not the same. As in the distribution, he adds, of marine fish, the interposition of a continent stretching from the tropics far into the temperate or colder parts of the ocean separate different ick theological groups. So with respect to the freshwater species, the intrusion of arms of the sea running far to the northwards or the interposition of a lofty mountain chain effects the same thing. The freshwater fish of the Cape of Good Hope and the South American ones are different from those of India and China, etc. Cuvier and Valencians in their Histoire des Poissants observe that very few species of fish cross the Atlantic, although their statement is correct, it's found that a great many species are common to the opposite sides of the Indian Ocean, inhabiting alike the Red Sea, the eastern coast of Africa, Madagascar, the Moratius, the Indian Ocean, the southern seas of China, the Malay Archipelago, the northern coasts of Australia, and the whole of Polynesia. This very wide diffusion, says Sir J. Richardson, may have been promoted by chains of islands running east and west, which are wanting in the deep Atlantic. An archipelago extending far in longitude favours the migration of fish by multiplying the places of deposit for spawn along the shores of islands and on intervening coral banks, and in such places also, fish find their appropriate food. The flying fish are found, some stragglers accepted, only between the tropics. In receding from the line, they never approach a higher latitude than the 40th parallel. The course of the Gulf Stream, however, and the warmth of its water, enable some tropical fish to extend their habitations far into the temperate zone. Thus the Chetidons, which abound in the seas of hot climates, are found among the Bermudas on the 32nd parallel, where they are preserved in basins enclosed from the sea, as an important article of food for the garrison and inhabitants. Other fish, following the direction of the same great current, range from the coast of Brazil to the banks of New Finland. All are aware that there are certain fish of passage which have their periodical migrations, like some tribes of birds. The salmon, towards the season of spawning, ascends the rivers for hundreds of miles, leaping up the cataracts which it meets in its course, and then retreats again into the depths of the ocean. The herring and the haddock, after frequenting certain shores, in vast shoals for a series of years, desert them again and resort to other stations, followed by the species which prey on them. Eels are said to descend into the sea for the purpose of producing their young, which are seen returning into the fresh water by myriads, extremely small in size, but possessing the power of surmounting every obstacle in the waters in the course of a river, by applying their slimy and glutinous bodies to the surface of rocks, or the gates of a lock, even when dry, and so climbing over it. Before the year 1800, there were no eels in Lake Väner, the largest inland lake in Sweden, which discharges its waters by the celebrated cataracts of Trollhattin. Eels have been informed by Professor Nilsen that since the canal was opened, uniting the river Goto with the lake, by a series of nine locks, each of great height, eels have been observed in abundance in the lake. It appears therefore that, though they were unable to ascend the falls, they have made their way by the locks, by which in a very short space of difference of level of 114 feet, is overcome. Gmellen says that the Ansarais, wild geese, docks, and others, subsist in their migrations on a spawn of fish, and that oftentimes, when they void the spawn, two or three days afterwards, the eggs retain their vitality unimpaired. When there are many disconnected freshwater lakes in a mountainous region, at various elevations, each remote from the other, it has often been deemed inconceivable how they could all become stocked with fish from one common source. But it has been suggested that the minute eggs of these animals may sometimes be entangled in the feathers of waterfowl. These, when a light to wash and plume themselves in the water, may often unconsciously contribute to propagate swarms of fish, which, in due season, will supply them with food. Some of the water beetles also, as the Ditisidae, are amphibious, and in the evening, quit their lakes and pools and flying in the air, transport the minute ova of fishes to distant waters. In this manner some naturalists of the Friya fish appearing occasionally in small pools caused by heavy rains. But the showers of small fish, stated in so many accounts to have fallen from the atmosphere, require further investigation. Geographical Distribution and Migrations of Testatia The Testatia, of which so great a variety of species occurs in the sea, are a class of animals of peculiar importance to the geologist, because their remains are found in strata of all ages, and, generally, in a higher state of preservation than those of other organic beings. Climate has a decided influence on the geographical distribution of species in this class. But as there is much greater uniformity of temperature in the waters of the ocean, then in the atmosphere which invests the land, the diffusion of marine mollusks is on a whole more extensive. Some forms attain their fullest development in warm latitudes, and are often exclusively confined to the torrid zone, as Nautilus, Harpa, Terabellum, Pyramidella, Delphinula, Aspergillum, Tridacna, Cuculia, Aracetala, Corbis, Perna, and Plecatula. Other forms are limited to one region of the sea, as the Trigonia to parts of Australia, and the Cancolepas to the western coast of South America. The marine species inhabiting the ocean, on the opposite sides of the narrow isthmus of Panama, are found to differ almost entirely, as we might have anticipated, since a West Indian mollusk cannot enter the Pacific without coasting round South America, and passing through the inclement climate of Cape Horn. The continuity of the existing lines of continent from north to south prevents any one species from belting the globe, or from following the direction of the isothermal lines. Currents also flowing permanently in certain directions, and the influx at certain points of great bodies of fresh water, limit the extension of many species. Those which love deep water are arrested by shoals. Others, fitted for shallow seas, cannot migrate across unfathomable abysses. The nature also of the ground has an important influence on the testacious fauna, both on the land and beneath the waters. Certain species prefer a sandy, others a gravelly, and some a muddy sea bottom. On the land, limestone is of all rocks the most favourable, to the number and propagation of species of the genera helix, clasilia, bulimus, and others. Professor E. Forbes has shown as the result of his labours in dredging the Aegean Sea, that there are eight well-marked regions of depth, each characterised by its peculiar testacious fauna. The first of these, called the Latoral Zone, extends to a depth of two fathoms only, but this narrow belt is inhabited by more than 100 species, the second region, of which 10 fathoms is the inferior limit, is almost equally populous, and a copious list of species is given as characteristic of each region down to the seventh, which lies between the depths of 80 and 105 fathoms. All the inhabited space below this, being included in the eighth province, where no less than 65 species of testacia have been taken. The majority of the shells in this lowest zone are white or transparent. Only two species of mollusca are common to all the eight regions, namely Archaeolactia and Cerithium lima, great range of some provinces and species. In Europe, conchologists distinguish between the Arctic fauna, the southern boundary of which corresponds with the isothermal line at 32 degrees Fahrenheit, and the Celtic, which commencing with that limit, as its northern frontier, extends southward to the mouth of the English Channel and Cape Finistere in France. From that point begins the Lusitainian fauna, which, according to the recent observations of Mr. Andrew 1852, ranges to the Canary Islands. The Mediterranean province is distinct from all those above enumerated, although it has some species in common with each. The Indo-Pacific region is by far the most extensive of all. It reaches from the Red Sea in the eastern coast of Africa to the Indian archipelago and joining parts of the Pacific Ocean. To the geologist, it furnishes a fact of no small interest by teaching us that one group of living species of mollusca may prevail throughout an area exceeding in magnitude the utmost limits we can as yet assign to any assemblage of contemporaneous fossil species. Mr. Cumming obtained more than a hundred species of shells from the eastern coast of Africa, identical with those collected by himself at the Philippines and in the eastern coral islands of the Pacific Ocean, a distance equal to that from pole to pole. Certain species of the genus Ianthena have a very wide range, being common to seas north and south of the equator. They are all provided with a beautifully contrived float which renders them buoyant, facilitating their dispersion and enabling them to become active agents in disseminating other species. Captain King took a specimen of Ianthena fragilis, alive, a little north of the equator, so loaded with barnacles, pentelasmus, and their ova that the upper part of its shell was invisible. The rock welk, perpura lapillus, a well-known British univalve, inhabits both the North Atlantic and North Pacific. Helix putris, succini aputris, so common in Europe, where it reaches from Norway to Italy, is also said to occur in the United States and in New Finland. As this animal inhabits constantly the borders of pools and streams, where there is much moisture, it is not impossible that different waterfowl have been the agents of spreading some of its minute eggs, which may have been entangled in their feathers. The freshwater snail, limneus palustris, so abundant in English ponds, ranges uninterruptedly from Europe to Kashmir, and thence to the eastern parts of Asia. Helix espersa, one of the commonest of our larger land shells, is found in St. Helena and other distant countries. Some conchologists have conjectured that it was accidentally imported into St. Helena in some ship. For it is an eatable species, and these animals are capable of retaining life during long voyages without air or nourishment. Perhaps no species has a better claim to be called cosmopolite than one of our British bivalves, Saxecava rugosa. It is spread all over the North Polar seas and ranges in one direction through Europe to Senegal, occurring on both sides of the Atlantic. While in another, it finds its way into the North Pacific, and thence to the Indian Ocean. Nor do its migrations seize until it reaches the Australian seas. A British brachyopod, named Terra Brachula, Kaput Serpentis, is common, according to Professor E. Forbes, to both sides of the North Atlantic and to the South African and Chinese seas. Confined range of other species. Mr. Lo, in a memoir published in the Cambridge Transactions in 1834, enumerates 71 species of land mollusca, collected by him in the islands of Madeira and Porto Santo, 60 of which belong to the genus Helix alone, including as subgenera, bolemus, and acatina, and excluding vitrina and clausilia. Forty-four of these are new. It is remarkable that very few of the above-mentioned species are common to the neighboring archipelago of the Canaries, but it is a still more striking fact that of the 60 species of the three genera above-mentioned, thirty-one are natives of Porto Santo, whereas in Madeira, which contains ten times the superfaces, were found by twenty-nine. Of these only four were common to the two islands, which are separated by a distance of only twelve leagues, and two even of these four, namely Helix, Porto Stoma, and H. Ventrosa, are species of general diffusion, common to Madeira, the Canaries, and the South of Europe. The confined range of these molluscs may easily be explained if we admit that species have only one birthplace, and the only problem to be solved would relate to the exceptions, to account for the dissemination of some species throughout several islands and the European continent. May not the eggs, when washed into the sea by the undermining of cliffs or blown by a storm from the land, float un-injured to a distant shore? Their mode of diffusion, notwithstanding the proverbial slow-motion of snails and molluscs in general, and although many aquatic species adhere constantly to the same rock for their whole lives, they are by no means destitute of provision for disseminating themselves rapidly over a wide area. Some mollusca, says Professor E. Forbes, migrate in their larva state, for all of them undergo a metamorphosis either in the egg or out of the egg. The gastropoda commends life under the form of a small spiral shell, and an animal furnished with ciliated wings, or lobes, like a pteropod, by means of which it can swim freely, and in this form can migrate with ease through the sea. We are accustomed to associate in our minds the idea of the greatest locomotive powers with the most mature and perfect state of each species of invertebrate animal, especially when they undergo a series of transformations. But in all the mollusca, the reverse is true. The young fry of the cockle, for example, cardium, possesses, when young, or in the larva state, an apparatus which enables them both to swim and to be carried along easily by a marine current. These small bodies here represented which bury considerable resemblance to the fry of the univalve or gastropotus shells above mentioned. Our so minute at first is to be just visible to the naked eye. They begin to move about from the moment they are hatched by means of the long cilia, placed on the edges of the locomotive disc or vellum. This disc shrinks up as they increase in size, and gradually disappears, no trace of it being visible in the perfect animal. Some species of shell-bearing mollusca lay their eggs in a sponge-like nidus, wherein the young remain enveloped for a time after their birth. And this buoyant substance floats far and wide as readily as seaweed. The young of other vi-viperous tribes are often born along entangled in seaweed. Sometimes they are so light, that like grains of sand, they can be easily moved by currents. Balany and circulae are sometimes found adhering to floating coconuts, and even to fragments of pumice. In rivers and lakes, on the other hand, aquatic univalves usually attach their eggs to leaves and sticks which have fallen into the water, and which are liable to be swept away during floods, from tributaries to the main streams, and from thence to all parts of the same basins. Particular species may thus migrate during one season from the headwaters of the Mississippi or any other great river to countries bordering the sea, at the distance of many thousand miles. An illustration of the mode of attachment of these eggs will be seen in the annexed cut, figure 100. The habit of some testacea, to adhere to floating wood, is proved by their fixing themselves to the bottoms of ships. By this mode of conveyance, mytilus polymorphus, previously known only in the Danube and Volga, may have been brought to the commercial docks in the Thames and to Hamburg, where the species is now domiciled, but Mr. Gray suggests that, as the animal is known to have the faculty of living for a very long time out of water, it is more probable that it was brought in Russian timber, than worn uninjured through the salt water at the bottom of a vessel. A lobster, astakis marinus, was lately taken alive, covered with living muscles, mytilus edulis, and a large female crab, cancer pegerus, covered with oysters, and bearing also Enomia aephipium and actinae, was taken in April 1832 off the English coast. The oysters, seven in number, include individuals of six years growth, and the two largest are four inches long and three inches and a half broad. Both the crab and the oysters were seen alive by Mr. Robert Brown. From this example we learn the manner in which oysters may be diffused over every part of the sea where the crab wanders, and if they are at length, carry to a spot where there is nothing but fine mud, the foundation of a new oyster bank may be laid on the death of the crab. In this instance the oysters survived the crab many days, and were killed at last only by long exposure to the air. Geographical Distribution and Migrations of Zoophytes Zoophytes are very imperfectly known, but there can be little doubt that each maritime region possesses species peculiar to itself. The madre pores, or lameliferous polyperia, are found in their fullest development only in the tropical seas of Polynesia and the East and West Indies, and this family is represented only by a few species in our seas. The zoophytes of the Mediterranean, according to Ehrenberg, differ almost entirely from those of the Red Sea, although only 70 miles distant. Out of 120 species of anthrozoa, only two are common to both seas. Peronum nesura, after studying the Holothuriae, Medusiae, and other co-geners of delicate and changeable forms, came to the conclusion that each kind has its place of residence determined by the temperature necessary to support its existence. Thus, for example, they found the abode of Pyrosoma Atlantica confined to one particular region of the Atlantic Ocean. Let us now inquire how the transportation of zoophytes from one part of the globe to another is affected. Many of them, as in the families Flustra and Certullaria, attach themselves to seaweed, and are occasionally drifted along with it. Many fix themselves to the shells of Molusca and are thus borne along by them to short distances. Others, like some species of sea pens, float about in the ocean and are usually believed to possess powers of spontaneous motion. But the most frequent mode of transportation consists in the buoyancy of their eggs, or certain small vesicles which are detached and are capable of becoming the foundation of a new colony. Gems, as they are called, have in many instances a locomotive power of their own by which they proceed in a determinate direction for several days after separation from the parent. They are propelled by means of numerous short threads or cilia, which are in constant and rapid vibration, and when thus supported in the water, they are borne along by currents to a great distance. That some zoophytes adhere to floating bodies is proved by their being found attached to the bottoms of ships, like certain Testatia before alluded to, geographical distribution and migration of insects. Before I conclude this sketch of the manner in which the habitable parts of the earth are shared out among particular assemblages of organic beings, I must offer a few remarks on insects, which by their numbers and the variety of their powers and instincts exert a prodigious influence in the economy of animate nature. As a large portion of these minute creatures are strictly dependent for their subsistence on certain species of vegetables, entomological provinces must coincide in considerable degree with the botanical. All the insects, say the trail, brought from the eastern parts of Asia and China, whatever be their latitude and temperature, are distinct from those of Europe and of Africa. The insects of the United States, although often approaching very close to our own, are with very few exceptions and are specifically distinguishable by some characters. In South America, the equinoctial lands of New Granada and Peru on the one side and of Guyana on the other contain for the most part distinct groups, the Andes forming the division and interposing a narrow line of severe cold between climates otherwise very similar. Migratory Instincts All the insects of the United States and Canada differ specifically from the European, while those of Greenland appear to be in a great measure identical with our own. Some insects are very local, while a few, on the contrary, are common to remote countries between which the poorer zone and the ocean intervene. Thus our painted Lady Butterfly, Vanessa Cardoui, reappears at the Cape of Good Hope and in New Holland and Japan, with scarcely a varying streak. The same species is said to be one of the few insects which are universally dispersed over the earth, being found in Europe, Asia, Africa and America, and its wide range is the more interesting because it seems explained by its migratory instinct seconded no doubt by a capacity enjoyed by a few species of enduring a great diversity of temperature. A vast swarm of this species, forming a column from ten to fifteen feet broad, was a few years since observed in the Canton Devaude. They traversed the country with great rapidity from north to south, all flying onwards in regular order, close together and not turning from their course on the approach of other objects. Professor Bonnelli of Turin observed in March of the same year a similar swarm of the same species also directing their flight from north to south, in Piedmont, in such immense numbers that at night the flowers were literally covered with them. They had been traced from Coney, Rackone, Sousa, etc. A similar flight at the end of the last centuries recorded by Mejur Louch in the memoirs of the Academy of Turin. The fact is the more worthy of notice because the caterpillars of this butterfly are not gregarious but solitary from the moment that they are hatched and this instinct remains dormant while generation after generation passes away till it suddenly displays itself in full energy when their numbers happen to be in excess. Not only peculiar species, but certain types distinguish particular countries and there are groups observed curvy which represent each other in distant regions whether in their form, their functions, or in both. Thus the honey and wax of Europe, Asia, and Africa are in each case prepared by bees congenerous with our common hive bee. While in America this genus is nowhere indigenous but is replaced by melapona, trigona, and euglosa and in New Holland by a still different but undescribed type. The European bee, apis mellifika, although not a native of the New World is now established both in North and South America. It was introduced into the United States by some of the early settlers and has since overspread the vast forests of the interior building hives in the decayed trunks of trees. The Indians, says Irving, consider them as the harbinger of the white man as the buffalo is of the red man and say that in proportion as the bee advances the Indian and the buffalo retire. It is said, continues the same writer that the wild bee is seldom to be met with at any great distance from the frontier and that they have always been the heralds of civilization preceding it as it advanced from the Atlantic borders. Some of the ancient settlers of the West even pretend to give the very year when the honeybee first crossed the Mississippi. The same species is now also naturalized in Van Demen's land and New Zealand. As almost all insects are winged they can readily spread themselves over their progress is not opposed by uncongenial climates or by seas, mountains and other physical impediments and these barriers they can sometimes surmount by abandoning themselves to violent winds which as I have before stated when speaking of the dispersion of seeds may in a few hours carry them to very considerable distances. On the Andes some Sphinxes and flies have been observed by Humboldt at the height of 19,180 feet above the sea and which appear to him to have been involuntarily carried into these regions by ascending currents of air. White mentions a remarkable shower of aphids which seem to have emigrated with an east wind from the great hop plantations of Kent and Sussex and blackened the shrubs and vegetables where they alighted at Selbourn, spreading at the same time in great clouds all along the Vale from Farnham to Alton. These aphids are sometimes accompanied by vast numbers of the common Ladybird, Cochonella septum punctata which feed upon them. It is remarkable, says Kirby, that many of the insects which are occasionally observed to emigrate as for instance the libalule, Cochonella, Carribee, Cicady, etc. are not usually social insects but seem to congregate like swallows merely for the purpose of emigration. Here therefore we have an example of an instinct developing itself on certain rare emergencies causing unsocial species to become ingregorious and to venture sometimes even to cross the ocean. The armies of locusts which darken the air in Africa and traverse the globe from Turkey to our southern counties in England are well known to all. When the western gales sweep over the pompous they bear along with them myriads of insects of various kinds. As a proof of the manner in which species may be thus diffused I may mention that when the Creole frigate was lying in the outer roads off Venice Aries in 1819 at the distance of six miles from the land her decks and rigging were suddenly covered by thousands of flies and grains of sand. The sides of the vessel had just received a fresh coat of paint to which the insects adhered in such numbers as to spot and disfigure the vessel and to render it necessary partially to renew the paint. Captain W. H. Smith was obliged to repaint his vessel the Adventure in the Mediterranean from the same cause. He was on his way from Malta to Tripoli when a southern wind blowing from the coast of Africa then one hundred miles distant drove such myriads of flies upon the fresh paint that not the smallest point was left unoccupied by insects. To the southward of the river plate off Cape St. Antonio and at the distance of fifty miles from land several large dragon flies alighted on the Adventure frigate during Captain King's late expedition to the Straits of Magellan. If the wind debates when insects are thus crossing the sea the most delicate species are not necessarily drowned for many can repose without sinking on the water. The slender long-leaded tipulae having been seen standing on the surface of the sea when driven out far from our coast took wing immediately on being approached. Exotic beetles are sometimes thrown on our shore which revive after having been long drenched in seawater and the periodical appearance of some conspicuous butterflies among us after being unseen some for five others for fifty years has been ascribed, not without probability to the agency of the winds. Inundations of rivers, observes Kirby if they happen at any season except in the depths of winter always carry down a number of insects floating on the surface of bits of stick, weeds, etc. so that when the water subside the entomologist may generally reap a plentiful harvest. In the dissemination moreover of these minute beings as in that of plants, the larger animals play their part. Insects are in numberless instances worn along in the coats of animals or the feathers of birds and the eggs of some species are capable, like seeds of resisting the digestive powers of the stomach and after they are swallowed with herbage may be ejected again unharmed in the dung. End of Section 88 Chapter 39 Part 2 of Principles of Geology This is a LibriVox recording or LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org Principles of Geology by Charles Lyle Section 89 Chapter 39 Laws which regulate the geographical distribution of species continued Part 2 Geographical Distribution and Diffusion of Man I have reserved for the last some observations on the range and diffusion of the human species over the earth the influence of man in spreading other animals and plants especially the terrestrial many naturalists have amused themselves in speculating on the probable birthplace of mankind the point from which if we assume the whole human race to have descended from a single pair the tide of immigration must originally have proceeded it has always been a favorite conjecture that this birthplace was situated within or near the tropics where perpetual summer rains and where fruits, herbs and roots are plentifully supplied throughout the year the climate of these regions it has been said is suited to a being born without any covering and who had not yet acquired the arts of building habitations or providing clothes Progress of Human Population The Hunter State it has been argued which Montesquieu placed the first was probably only the second stage to which mankind arrived since so many arts must have been invented to catch a salmon or a deer that society could no longer have been in its infancy when they came into use When regions with the spontaneous fruits of the earth abound became over-peopled men would naturally diffuse themselves over the neighboring parts of the temperate zone but a considerable time would probably elapse before this event took place and it is possible, as a writer before sighted observes that in the interval before the multiplication of their numbers and their increasing wants had compelled them to emigrate some arts to take animals were invented but far inferior to what we see practiced at this day among savages as their habitations gradually advanced into the temperate zone the new difficulties they had to encounter would call forth by degrees the spirit of invention and the probability of such inventions always rises with the number of people involved in the same necessity A distinguished modern writer who coincides for the most part in the views above mentioned has introduced one of the persons in his second dialogue as objecting to the theory of the human race having gradually advanced from a savage to a civilized state on the ground that the first man must have inevitably been destroyed by the elements or devoured by savage beasts so infinitely his superiors and physical force he then contends against the difficulty here started by various arguments, all of which perhaps superfluous for if a philosopher is pleased to indulge in conjectures on this subject why should he not assign, as the original seat of man some of those large islands within the tropics which are as free from large beasts of prey as Van Diemen's land or Australia here man may have remained for a period peculiar to a single island just as some of the large anthropomorphous species are now limited to one island within the tropics in such a situation the newborn race might have lived in security though far more helpless than the new Holland savages and might have found abundance of vegetable food colonies may afterwards have been sent forth from this mother country and then the peopling of the earth may have proceeded according to the hypothesis before alluded to to form a probable conjecture respecting the country from whence the early civilization of India was derived has been found almost as difficult as to determine the original birthplace of the human race that the dawn of oriental civilization did not arise within the limits of the tropics is the conclusion to which Baron William von Humboldt has come after much patient research into the diversities of the structure of language and their influence on the mental development of the human race according to him the ancient Zend country from whence the spread of knowledge and the arts has been traced in a south-easterly direction lay to the northwest of the Upper Indus as to the time of the first appearance of man upon the earth if we are to judge from the discordance of opinion amongst celebrated chronologies not even a rude approximation has yet been made towards determining a point of so much interest the problem seems hitherto to have baffled the curiosity of the antiquary if possible more completely than the fixing on a geographical site for the original habitation of the ancestors of the human race the Chevalier Bunsen in his elaborate and philosophical work on ancient Egypt has satisfied not a few of the learned by an appeal to monumental inscriptions still extant that the successive dynasties of kings may be traced back without a break to meanies and that the date of his reign would correspond with the year 3640 BC he supposes at the same time what is most reasonable that the Egyptian people must have existed for a long period probably at least for five centuries and there earlier and less settled state before they reached the point of civilization at which meanies consolidated them into a great and united empire this would carry us back to upwards of 4000 years BC or to an epic coincident with that commonly set down for the creation of the world in accordance with computations founded on the combined ages of the successive anti-Diluvian patriarchs it follows that the same epic of meanies is anterior by a great many centuries to the most ancient of the dates usually fixed upon for the mosaic deluge the fact that no record or tradition of any great and overwhelming flood has been detected in the mythology or monumental annals of the Egyptians will suggest many reflections to a geologist who has weighed well the evidence we possess of a variety of partial deluges which have happened in districts not free like Egypt for the last 3000 years from earthquakes and other causes of great aqueous catastrophes the tales and legends of calamitous floods preserved in Greece, Asia Minor the southern shores of the Baltic, China, Peru and Chile have as we have seen been all of them handed down to us by the inhabitants of regions in which the operation of natural causes in modern times and the recurrence of a succession of disastrous floods afford us data for interpreting the meaning of the obscure traditions of an illiterate age in his learned treatise on ancient chronology Dr. Hales has selected from a much greater number a list of no less than 120 authors all of whom give a different period for the epic of the creation of the world the extreme range of difference between them amounting to no less than 3268 years it appears that even amongst authorities who in England are generally regarded as orthodox there is a variance not of years or of one or two centuries but upwards of a millennium according as they have preferred to follow the Hebrew or the Samaritan or the Greek versions of the Mosaic writings can we then wonder that they who decipher the monuments of Egypt or the geologists who interpret the earth's autobiography should arrive at views respecting the date of an ancient empire or the age of our planet irreconcilable with every one of these numerous and conflicting chronologies the want of agreement amongst the learned in regard to the probable date of the deluge of Noah is a source of far greater perplexity and confusion than our extreme uncertainty is to the epic of the creation the deluge being a comparatively modern event from which the re-peopling of the earth and the history of the present races of mankind is made to begin naturalists have long felt that to render probable the received opinion of all the leading varieties of the human family have originally sprung from a single pair a doctrine against which there appears to me to be no sound objection a much greater lapse of time is required for slow and gradual formation of races such as the Caucasian, Mongolian and Negro that is embraced in any of our popular systems of chronology the existence of two of those marked varieties above mentioned can be traced back three thousand years before the present time or to the paintings of pictures preserved in the tombs or on the walls of buried temples in Egypt in these we behold the Negro and Caucasian physiognomies portrayed as faithfully and in a strong contrast as if the likeness of those races have been taken yesterday when we consider therefore the extreme slowness of the changes which climate and other modifying causes have produced in modern times we must allow for a vast series of antecedent ages in the course of which the long continued influence of similar external circumstances gave rise to peculiarities probably increased in many successive generations until they were fixed by hereditary transmission the characteristic forms and features thus acquired by certain tribes may have been afterwards diffused by migration for a few centers over wide continental spaces the theory therefore that all the races of man have come from one common stock receives support from every investigation which forces us to expand our ideas of the duration of past time or which multiplies the number of years that have passed away since the origin of man hitherto geology has neither enlarged nor circumscribed the human period but simply proved that in the history of animated nature it is comparatively modern or the last of a long series of antecedent epics in each of which the earth has been successively peopled by distinct species of animals and plants in an early stage of society the necessity of hunting acts as a principle of repulsion causing men to spread with the greatest rapidity over a country until the whole is covered with scattered settlements it has been calculated that eight hundred acres of hunting ground produce only as much food as half an acre of arable land when the game has been in a great measure exhausted and a state of pasturage succeeds the several hunter tribes being already scattered may multiply in a short time into the greatest number which the pastoral state is capable of sustaining the necessity, says Bran thus imposed upon the two savage states of dispersing themselves far and wide over the country affords a reason why at a very early period the worst parts of the earth may have become inhabited but this reason it may be said is only applicable in as far as regards the peopling of a continuous continent whereas the smallest islands however far remote from continents have almost always been found inhabited by man St Helena, it is true, afforded an exception for when that island was discovered in 1501 it was only inhabited by seafowl and occasionally by seals and turtles and was covered with a forest of trees and shrubs all of species peculiar to it with one or two exceptions and which seems to have been expressly created for this remote and insulated spot the islands also of Mauritius Bourbon, Pitcairns and Juan Fernandez and those of the Galapagos Archipelago one of which is 70 miles long were inhabited when first discovered and what is more remarkable than all the Falkland Islands which together are 120 miles in length by 60 in breadth and a bounding in food fit for the support of man drifting of canoes to vast distances but very few of the numerous coral islets and volcanoes of the vast Pacific capable of sustaining a few families of men have been found untenanted and we have therefore to inquire whence and by what means if all the members of the great human family have had one common source could those savages have migrated Cook, Foster and others have remarked that parties of savages in their canoes must have often lost their way and must have been driven on distant shores where they were forced to remain deprived both of the means and of the requisite intelligence for returning to their country thus Captain Cook found on the island of Watio three inhabitants of Ota-hate who had been drifted thither in a canoe although the distance between the two aisles is 550 miles in 1696 two canoes containing 30 persons who had left Encorso were thrown by contrary winds and storms on the island of Samar one of the Philippines at a distance of 800 miles in 1721 two canoes one of which contained 24 and the other six persons men, women and children were drifted from an island called Faroelap to the island of Guam one of the Marians a distance of 200 miles Kotsubiu when investigating the coral aisles of Radak at the eastern extremity of the Caroline aisles became acquainted with a person of the name of Kadu who was a native of Ulia an isle 1500 miles distant from which he had been drifted with a party Kadu and three of his countrymen one day left Ulia in a sailing boat when a violent storm arose and drove them out of their course they drifted about the open sea for eight months according to their reckoning by the moon making a knot on a cord at every new moon being expert fishermen they subsisted entirely on the produce of the sea and when the rain fell laid in as much fresh water as they had vessels to contain it Kadu says Kotsubiu who was the best diver frequently went down to the bottom of the sea where it is well known that the water is not so salt with a coconut shell with only a small opening when these unfortunate men reached the aisles of Radak every hope and almost every feeling had died within them their sail had long been destroyed their canoe had long been the sport of winds and waves and they were picked up by the inhabitants of Or in a state of insensibility but by the hospitable care of these islanders they soon recovered and were restored to perfect health Captain Bichi in his voyage to the Pacific fell in with some natives of the Coral Islands who had in a similar manner been carried to a great distance from their native country they had embarked to the number of 150 souls in three double canoes from Anna or Chain Island situated about 300 miles to the eastward of Otehati they were overtaken by the monsoon which dispersed the canoes and after driving them about the ocean left them be calmed so that a great number of persons perished two of the canoes were never heard of but the other was drifted from one uninhabited island to another at each of which the voyagers obtained a few provisions and at length, after having wandered for a distance of 600 miles they were found and carried to their home in the Blossom Mr. Crawford informs me that there are several well authenticated accounts of canoes having been drifted from Sumatra to Madagascar and by such causes a portion of the Malayan language with some useful plans have been transferred to that island which is principally peopled by Negroes the space traversed in some of these instances was so great that similar accidents might suffice to transport canoes from various parts of Africa to the shores of South America or from Spain to the Azores and thence to North America so that man, even in a rude state of society is liable to be scattered involuntarily by the winds and waves over the globe in a manner singularly analogous to that in which many plants and animals are diffused we ought not then to wonder that during the ages required for some tribes of the human race to attain that advanced stage of civilization which empowers the navigator to cross the ocean in all directions with security the whole earth should have become the abode of rude tribes of hunters and fishers were the whole of mankind now cut off with the exception of one family inhabiting the old or new continent or Australia or even some coral islet of the Pacific we might expect their descendants though they should never become more enlightened than the South Sea islanders or the Esquimo to spread in the course of ages over the whole earth diffused partly by the tendency of population to increase in a limited district beyond the means of subsistence and partly by the accidental drifting of canoes by tides and currents to distant shores involuntary influence of man in diffusing animals and plants many of the general remarks which have been made respecting the influence of man in spreading or in checking the diffusion of plants apply equally to his relations with the animal kingdom on a future occasion I shall be led to speak of the instrumentality of our species in naturalizing useful animals and plants in new regions when explaining my views of the effects which the spreading and increase of certain species exert in the extirpation of others at present I shall confine myself to a few remarks on the involuntary aid which man lends to the dissemination of the species in the mammiferous class our influence is chiefly displayed in increasing the number of quadrupeds which are serviceable to us and in exterminating or reducing number of those which are noxious sometimes however we unintentionally promote the multiplication of inimical species as when we introduced the rat which was not indigenous in the new world into all parts of America they have been conveyed over in ships and now infest a great multitude of islands and parts of that continent in like manner the Norway rat Mustekumanus has been imported into England where it plunders our property in ships and houses among birds the house sparrow may be cited as a species known to have extended its range with the tillage of the soil during the last century it has spread gradually over Asiatic Russia towards the north and east always following the progress of cultivation it made its first appearance on the ear-titch in Tobolsk soon after the Russians had plowed the land it came in 1735 up the obi to Beresau and four years after to Narin about 15 degrees of longitude farther east in 1710 it had been seen in the higher parts of the coast of Lena in the government of Irkutsk in all these places it is now common but is not yet found in the uncultivated regions of Kamchatka the great viper Fair Delance a species no less venomous than the rattlesnake which now ravages Martinique and St. Lucia was accidentally introduced by man and exists in no other part of the West Indies many parasitic insects which attack our persons and some of which are supposed to be peculiar to our species have been carried into all parts of the earth and have as high a claim as man to a universal geographical distribution a great variety of insects have been transported in ships from one country to another especially in warmer latitudes the European housefly has been introduced in this way into all the South Sea islands notwithstanding the coldness of our climate in England we have been unable to prevent the cockroach Blata Orientalis from entering and diffusing itself in our ovens and kneading troughs and availing itself of the artificial warmth which we afford it is well known also that beetles and many other kinds of lignopurdice insects have been introduced into Great Britain in timber especially several North American species the commercial relations says Malta Brune between France and India have transported from the latter country the aphis which destroys the apple tree and two sorts of niraptura the lucifuga and flavocola mostly confined to province and the neighborhood of Bordeaux where they devour the timber in the houses and naval arsenals among mollusks we mentioned the Tirito Navalis which is a native of equatorial seas but which by adhering to the bottom of ships was transported to Holland where it has been most destructive to vassals and piles the same species has also been naturalized in England and other countries by employing an extensive commerce Bulimus undatus a land species of considerable size native of Jamaica and other West Indian islands has been imported adhering to tropical timber into Liverpool and as I learned from Mr. Broderick is now naturalized in the woods near that town and all these and innumerable other instances are the involuntary agency of man as strictly analogous to that of the inferior animals like them we unconsciously contribute to extend or limit the geographical range and numbers of certain species in obedience to general rules in the economy of nature which are for the most part beyond our control End of section 89