 Section 0 of The Science, History of the Universe, Volume 6. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Recording by Nikalia Schwartz, Shenzhen, China. The Science, History of the Universe, Volume 6, edited by Francis Ralt Wheeler. Introduction Under favorable conditions, the study of animal life becomes not only profitable to mankind, but also as musical, as Apollo's loot. To know the animal life of the world is to know the world. It is impossible for an intelligent mind to grasp the principal animal forms of a given country without, at the same time, acquiring a great store of knowledge of that country's topography, soil, climate, and people. The love of wildlife springs eternal in the human breast. It is as natural for every child to be interested in animals as it is for every child to love the sound of music. Sad to say, however, that natural love for zoology often is completely stifled or warped out of shape by lack of opportunity. Those who, by force of circumstances, are compelled to grow up and live out their lives without knowing the satisfaction that is derived from an intimate acquaintance with at least one section of animal life lose much pleasure to which they legitimately are entitled. At no time in the history of the world has zoological knowledge been so vitally important to mankind as it is today. As animal life rapidly diminishes, its economic value to man becomes more apparent. Fifty years ago the edible fishes, lobsters, oysters, and clams were so abundant that no one found it necessary to delve deeply into the life history of any one of those groups. Today, and for the future, only the most careful conservation and cultivation based on precise zoological knowledge can preserve to man a continuous supply of those valuable and delicious foods. For twenty-five years the nation and the state have been studying ichthyology earnestly and diligently in pursuance of their costly and toilsome efforts to keep up the great food supply of the poor, the edible fishes. The demand in the United States for a flesh food supply that is cheaper than mammalian meat now engages the efforts of more than two hundred thousand men, backed by sixty million dollars of capital, and the animal fish product has a value of about fifty million dollars. Each year about one thousand four hundred million fish eggs and live fishes are distributed by the United States Bureau of Fisheries. Verily ichthyology is something more than a mere pastime for the angler or the student. Today it is on the same basis of human necessity as is the growing of wheat and corn. Fifty years ago few persons in America gave thought to the study of insects, save as a pastime. During recent years the ravages of insects have called forth a grand army of entomologists, first to study the destroyers and then to fight them. Today every farmer and fruit grower, every forester and every park superintendent is engaged in the great irrepressible conflict that is being waged between man and the insect world for the possession of the fruits, the vegetables and the trees that are as necessary to this earth as is the air we breathe. The monthly bulletins of the state economic zoologist of Pennsylvania painfully bring home to us the appalling extent and the fierceness of the battle for the trees. Verily the study of entomology has come to us to stay. For twenty years the United States government has been engaged in a continuous effort to inform all the people of the United States that the wild birds are man's most valuable friends and allies in his warfare against insect and mammalian pests. Some communities hearkened gladly to the message and responded with reasonable promptness to the efforts of the bird lovers in behalf of protective bird laws. A few states remained hostile to bird laws until the cotton ball weevil and other pests sharply brought home to their people the fact that they needed the assistance of the birds. Now that man's heedless and ignorant destructiveness has accomplished the extinction during our own times of a score of important animal species and today is threatening to annihilate many others, zoological knowledge has suddenly become a practical necessity. Both to the statesmen and to the citizen the protection of wildlife has become a solemn duty. Ignorance is dangerous alike to our forests and streams and to our wildlife. The time has long passed wherein it was necessary to justify by argument the existence of museums and the study of zoology. The nature study courses in our secondary schools testify abundantly to the public recognition of the need for the dissemination of zoological knowledge. Unfortunately however the workers in that field are as yet blindly groping for the methods by which they may impart to the school pupils of America the precise and practical animal lore that they need and desire. Today the nature study teachers elect to relegate to the background the great system of nature in favor of a few actual objects in the classroom which the pupil can handle and dissect and uses a foundation of original pupil philosophy. But the case is not wholly hopeless for the present situation is so bad that it cannot long endure. After long and unsatisfactory contemplation of study courses that mix together all sorts of living creatures and one chaotic mass it is a pleasure to take up a scholarly work in which the methods of nature are fully recognized and clearly set forth. Herein the foundation stones of nature are assembled and well and truly laid. Fortunate is the young naturalist and likewise the general reader of animal lore who early acquires the habit of broad generalization. I am tempted to call it the bird's eye view habit. Had I but one chance to send a message to the young naturalists of the world that message would be this lay out for yourselves a broad foundation of systematic knowledge and after that each stone of the structure will find its own permanent place as joyously as running water seeks the lowest level. It is impossible to insist too strongly upon the absolute vital necessity of conforming all zoological studies with the great system of nature. He who attempts to study any small group of animal forms without first gaining a bird's eye view of the surrounding territory and becoming familiar with the zoological grand divisions that lie around him loses much. It is a mastery of the grand divisions the orders families and genera in particular that lends the greatest charm to the study of zoology. The librarian who expects to store 10,000 books in such a manner that each one may be instantly available wisely provides 25 alcoves and 250 shelves and thereafter each new accession of books is a source of joy because the place for each volume is ready. The young naturalist without a zoological foundation is like a librarian who has no shelves and must create a place for each new book. But after all systematic zoological arrangement or classification is only to be regarded as a ready means to the accomplishment of more important ends Today the world is keenly concerned in the philosophy of animal life, its whys and its wherefores. A well thought out exposition of the origin and relationship of animals offers an excellent foundation for studies of species and of the habits and mental processes of individuals that shall continue and furnish human interests as long as any wildlife remains upon the earth. The old question, where does the animal belong? Has now as a running mate the ever present query, what does it think and do? The latter offers to every intelligent human being a delightful field of study and research. The new question, do animals reason, is no longer a question saved with the very few persons to whom the animal kingdom is mostly unknown territory. All the men who are best acquainted with the living wild animals of the world assert as one man that all animals think and reason, that some think very little, others much, and that some animals have reasoning facilities that are superior to those of some men. During recent years the work of our paleontologists has been profoundly fruitful. In America the rocks of the western badlands have yielded an extinct fauna of a character so marvellous as to be almost incredible until the actual remains are seen. It is quite beyond the power of words to convey adequate conceptions of the reptilian giants that formed the group of dinosaurs. The Brontosaurus, the Diplodocus, the Triceratops, the Stegosaurus, and the Tyrannosaurus almost be seen in order that the wonders of them may be appreciated. The story of the Jurassic Age in North America, as told by those gigantic remains, is sufficient to awe the most frivolous mind. In the presence of those vast skeletons, some of them so colossal that even the largest elephants of the present day seem small, the thoughtful observer finds a new realm of knowledge opening before him like a panorama. The animal kingdom takes on a solemn dignity and vastness never known before. Naturally the mind reaches out, octopus-like, to fasten tentacles upon the past and link it to the present. There is one result of zoological knowledge that no man can adequately set forth in words. It is the unending satisfaction and at times the delight that comes throughout the journey of life to every person who is able to recognize the most important animals that are met by the way. Except in mid-air, it is well nigh impossible for man to travel so far that he leaves behind him all visible forms of animal life. I believe this has been accomplished only by the men who have pressed nearest to the poles through the utmost cold. He who knows the wild animals of the world always travel among friends and in every land he finds a welcome. To him the whole world is interesting. To his pleasure in life thousands of beasts, birds and creeping things contribute. Nature's multitude of interesting forms stimulate his efforts to acquire knowledge and her fields of research come the nearest to revealing the fountains of perpetual youth. Today the life of the ardent nature lover is filled with activities. On the one hand there is the balance of nature to preserve and on the other that lost balance is to be restored. Those who are not engaged in fighting the noxious forms of animal life are commonly found on the firing line of the army that is fighting the perpetual war with those who would if let alone exterminate all wild creatures from the whole earth. Let us hope that millions of intelligent Americans will learn to appreciate more fully the splendid fauna of this continent in time to save it from the forces that now threaten it with annihilation. William T. Hornaday End of Section 0 The Science History of the Universe Volume 6 Edited by Francis Rold Wheeler Zoology Chapter 1 Fabulous Zoology The beginnings of Zoology lie in the region of Fable. In the earliest traditions and myths of primitive races the world is peopled with men and animals. Some real, some half real, some entirely fabulous. Natural and supernatural are mingled together and a religious or superstitious significance attaches to both real and unreal beings seen or imagined by primitive man. His ready imagination and uncritical belief made the creations of his fancy seem as real as those of his observation and experience. With the increase of knowledge of the real the unreal became more and more relegated to the domain of folklore and fable. Some of it has been preserved in the traditions and myths of different races some crystallized in the fanciful animals of decorative sculptures, paintings and heraldry. Most of it has been forgotten. It has been well observed that the imagination of man does not really enable him to create anything new but only to recombine or rearrange what he has seen. He may combine the body of a reptile with the wings of an eagle he may combine the head and shoulders of a man with the body and legs of a horse or attach to a human form the white wings of a swan he may infancy in larger mouths to the size of an elephant or conceive of a serpent large enough to encircle the whole world he may support the universe upon the back of an elephant of appropriate size but all these are not new creations they are objects known to his experience but recombined or altered in proportions it is only as he comes to realize with wider knowledge that certain combinations of parts, certain relations of size do not occur in nature that his imaginary beings become improbable or impossible he is accustomed to supply the missing parts of half-seen animals from his previous observations he sees the head of a deer projecting from the leafy wall of the forest and all unconsciously pictures the rest of the quadruped from what he has seen before he sees a distant eagle perched upon a crack and knows well enough that when it starts to fly it will stretch out a pair of broad wings now closely folded against a body and invisible in the distance if then he sees dimly outlined in the clouds a human form what more natural than to supply it with the long feathered wings that belong to the birds of the air or if at night with the wings of the bats that infest his cave dwelling nearly all of the fabulous monsters of zoology belong to this early period they have been handed down conventionalized in form and degenerated into fable but originally they were just as real as the rest of the half-seen half-imagined world in which primitive man existed perhaps the most familiar and universally known of these fabulous animals is the dragon it appears in all the older myths of the western nations in serpent form usually winked often with fiery or pestilential breath the deadly enemy and scourge of man it is equally prominent among the eastern peoples and probably received from them its conventional form the long hind legs the great eagle claws the body covered with glittering armor scales the writhing tail and bat-like wings among the Mediterranean nations it appears first as a sea monster and comes up out of the sea wings were a later addition in the northern myths it is at first a worm i.e. a serpent of gigantic size and the conventional form is borrowed later from the east the fabulous dragon had a real counterpart singularly close in some respects in the extinct carnivorous dinosaurs of the age of reptiles these gigantic reptiles were not winked indeed but in the proportions of body limbs and tail in the huge head and sharp teeth the enormous sharp eagle-like claws possibly even in the glittery scaly armor some of them at all events might have sat for a very tolerable portrait of the dragon of mythology it is a tempting explanation to suppose that some tradition of these real monsters handed down from primitive ancestors was the basis of the dragon legends so widely scattered among all races of men but this theory must be regretfully abandoned when the perspective of the geologic record is examined the last of the dinosaurs became extinct at the end of the Cretaceous period some three million years ago at a moderate estimate before the evolution of the various races of modern quadrupeds had begun long before monkeys and apes had evolved out of the primitive lemur-like animals from which they had arrived and long, long before the evolution of man the remote ancestors of the human race and the days of the dinosaurs were tiny shrew-like animals inferior in intelligence to almost any living quadrupeds and millions of years were to elapse before they slowly evolved a higher intelligence and finally became capable of articulate speech so it is utterly impossible that a tradition could have been handed down from the time when dinosaurs really existed nor is it to be supposed that the dragon myths are based upon discovery of their fossil remains for in the millions of years that have elapsed since their time the sand and mud in which their remains were buried have been converted into hard sandstone and shale and the bones so thoroughly petrified that they appear much like the rock itself they would not easily be recognized as bones at all and it would be quite out of the question for primitive man to get any correct notion of the kind of animals they represented if they happened to come across a few fragments unearthed out of the rock dinosaur bones may conceivably pass for bones of giants but the concept of the dragon could not possibly be founded upon them there remains a third explanation that in some region of the world dinosaurs might have survived until more recent times and have been seen by primitive men but from what is known of the geological history of life this supposition is so exceedingly improbable as to amount to an utter impossibility one is obliged to conclude that the dragon is wholly a creation of the imagination of man its source being probably among the races of eastern Asia how and why it came to assume its present conventional form would require a broad knowledge of the early history and mythology of these races to discern in the traditions of the northern races the dragon legends are engrafted upon the myth of the giant serpent the worm which in the old Norse story encircles the earth lying at the bottom of the surrounding ocean this same myth in another form is handed down as the sea serpent sea serpents however are easier to credit than dragons partly because less is known about the inhabitants of the sea than those of the land partly because among the multitudinous forms of ocean life there are many that correspond more or less with the preconceived idea of what a sea serpent ought to be like so that while the dragon is confined to legend and no one professes to have really seen one there be many down to the passengers on modern ocean liners who have testified to seeing a sea serpent of approved type sometimes it may be one of the large sea snakes sometimes a ribbon fish or a school of porpoises following one another as they leap out of the water so as to give the impression of the rolling coils of a great serpent sometimes a long streamer or a tangle of seaweed may look like the giant serpent with its main neck which all expect to see possibly among the unknown inhabitants of the great deep some such animal may really exist but until it is captured and its remains deposited in some museum of natural history it must be ranked upon fabulous monsters the unicorn of classical writers was a real animal the great one horned rhinoceros of India well known to eastern writers and not unfamiliar to the patrons of the Greek or Roman circuses in medieval Europe it suffered a curious transformation the northern artist had never seen a rhinoceros nor talked with anyone who had he knew that it was a great four-legged beast with a long horn on its forehead and the traditional foe of the lion so he crafted the twisted tusk of a gnar wall on the forehead of a horse and in this form it was conventionalized in heraldry it was not recognized when centuries later the rhinoceros was reintroduced to the knowledge of western nations the various composite monsters of the mythology of different races the centaurs and sirens of the Greeks the mermaids and swan maidens of western Europe the winged bulls of Assyria or the eagle-headed golds of Egypt have all a more or less definite religious significance and are theological rather than zoological myths some of them have survived in zoological lore supported like the sea serpent by the occasional sight of animals more or less resembling what the observer expected to see and their described appearance colored by the traditional description mermaids appear every now and then in the accounts of medieval writers some of the stories may well have been based on the manatee or dugong while in more recent years actual specimens of stuffed mermaids manufactured by the ingenious Japanese from the four part of a monkey and the tail of a fish have often been exhibited to another class of zoological myths belong the innumerable fanciful stories told of the characters and habits of real animals of the transmutation of men into animals and vice versa and of the transformation of one species of animal into another real metamorphosis of form as of the tadpole into the frog or of the larvae into the perfect insect is well known to more than natural history but however much or little the primitive ancestry may have known about it there seems to be no good reason to believe that the enchantment transformations of mythology originated in any real observations of metamorphosis in nature dream experiences imperfectly separated from the recollections of waking hours had probably much to do with their conception hence it would seem that while natural history possesses relations which may throw its beginnings to the fabulous monsters of ancient times the same cannot be said for the science of zoology which as a science requires evidence and having classified that evidence is lost to admit therein such mythical creatures who are undoubted aliens end of section one section two of the science history of the universe volume six this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Melanie Young the science history of the universe volume six edited by Francis Rowe Wheeler zoology development and distribution the animal kingdom includes a vast variety of organisms whose common basis of life is the cell they are like plants an organized community of cells the various members of this community are adapted to perform different services and many groups have specialized each for its particular function so that the individual cells are no longer capable of a separate life the animal or plant is thus not a mere aggregate of living cells but an organism any successive classes and orders of animals from lowest to highest there is a progressive complexity in the organism a more and more absolute and exact limitation of the cells or groups of cells to special functions this progressive specialization is the key to the life history of the individual organism the development or ontogeny of the animal and to the life history or phylogeny of the race all animals are to be regarded then as organized communities the units of these communities being protoplasm cells are originally identical in structure and capable of all the necessary activities of life but specialized to perform particular functions the first steps in the plan of organization as they appear in the development of the individual are identical in all animals the cell divides and re divides until it forms an aggregate of numerous small cells the blastula this aggregate continuing to subdivide then takes on a thimble like form the gastrilla one layer of cells lining the cavity the other being external this cavity is primarily to contain and digest food and the cells lining it naturally take on the functions of nutrition while the outer cells in contact with the outside world take on the functions of sensation of offense and defense and procuring food the living sponges and hydroids illustrate this stage of development more or less modified the next important stage in development is the formation of a third intermediate layer of cells between the inner layer or endoderm and the outer layer or ectoderm from this intermediate layer are developed in the higher animals the muscles circulatory system and various glands and organs the alimentary system with its glands being developed from the endoderm the skin the nervous system and the organs of sensation from the ectoderm from this point onward fundamental differences are to be found in the plan of organization of the principal types of animals and the organs adapted to serve the same purposes are often developed from different parts and in a different manner it is upon these fundamental differences in organization that the classification of the animal kingdom is based these lower animals are derived from the same stock as the higher ones they persist today because they are perfectly adapted to their habitat and mode of life or because they have gotten into a groove of evolutionary progress which did not allow them to advance so fast or so far as the higher types or because of arrested development from obscure causes some of the factors which have limited their evolution are clearly seen others are and perhaps always will be difficult to trace life originated in the ocean or at all events in water but the dry land environment has stimulated a higher evolution the obvious cause being the more abundant supply of oxygen admitting of more active life in order to preserve the form and relations of their parts all animals of any considerable size have been compelled to develop a rigid framework or skeleton of some kind the material and position of this skeleton and its further use for purposes of offense and defense have profoundly influenced the further development of the race in the lower animals the skeleton is generally external and the insects may be considered as representing the highest possibilities of a development based upon an external skeleton in the vertebrates the skeleton at first was mainly external but this became gradually replaced by an internal structure and the higher possibilities of development with the internal skeleton form one leading cause for the higher development and greater size attained by vertebrated animals the third and perhaps the most important factor in causing or arresting evolution is in the nature of the environment whether constant from age to age or subject to slow, secular or periodic change during geological time if an animal is fitted to its mode of life and the conditions of its immediate surroundings remain unchanged the organism has no occasion to vary and tends to become fixed and unprogressive but if the conditions are slowly changing the race must become adapted to fit its new environment and will retain or acquire a variability which through the influence of selection will lead to greater progressiveness the uniform and unchanging conditions of the deep sea have not been favorable to progress the theater of evolution of marine organisms has been the ever-changing littoral region the shores of the ocean advancing and retreating through successive geological periods widely varied in character ranging from rocky coast to sandy shoals or from muddy flats to the still clear water of protected inlets some of the deep sea organisms such as protozoans and sponges have remained unchanged so far as is known from the earliest geological periods down to the present day others like the crinoids or sea lilies long since extinct in the littoral region have found in the ocean depths a refuge where they still survive others again like the deep sea fishes originally adapted to the life of the shore have become curiously modified to suit the conditions of the oceans depths easily evident likewise is a corresponding difference between freshwater and land animals there can be no doubt that all terrestrial life was ultimately derived from an aquatic ancestry those animals which have solved the problem of the utilization of the more abundant oxygen supply of the air instead of the limited amount available in the water having been able to assume a higher development and greater progressiveness and the snails among mollusk the insects among arthropods and the reptiles, birds and mammals among vertebrates are the highest types in their respective classes the freshwater animals more limited in possibilities of development and subject to less change in variation in their conditions of life are of inferior type and as in the deep sea among them may be noted survivals of very ancient and primitive organisms and higher types developed upon the land but re-adapted to aquatic life having once acquired the capacity to use the oxygen of the air however they are careful not to lose it again and remain air breathers however far their adaptation to aquatic or marine life may be carried in other respects it will have been noted that reference has been made to the ancient forms of life thousands of varieties of which passed out of existence long before the existence of man and it is natural to ask by what means their nature is learned to reply by fossils without determining what a fossil is would be to beg the question the term fossil which originally meant merely things dug out of the ground has come to have a much more definite and restricted meaning in the language of modern science fossils are the remains of animals or plants or indications of their former existence found buried in the soil or enclosed in the rock in general only the hard parts of animals are preserved the shells of mollusks and crustaceans and the bones of the vertebrate animals while the fact that they are preserved at all is due to a combination of favorable circumstances usually when an animal dies the flesh or soft parts decay or are devoured the hard parts last longer but gradually disintegrate into formless dust or mud under the influence of the atmosphere or the air bearing waters of the surface but if the animal is buried in a swamp, a river bottom, lake or estuary where sediment is being piled up by the action of the rivers or of the sea its hard parts may be covered up in time to escape destruction to get below the zone of atmospheric influence in this case the remains will be subject only to the influence of the mineralized waters that permeate the soil and rocks beneath the surface the action of these waters is to dissolve particle by particle the organic matter of the fossil and to replace it with mineral matter in this process known as petrifaction usually the structure is preserved as well as the external form the bone or shell is thus converted wholly into stone solid and permanent like the sediment in which it was buried now converted by the same agencies into rock this is the ordinary process by which fossils are made there is nothing mysterious about it it is merely the natural result that water seeping upward toward the surface loaded with mineral matter and destitute of organic matter tends to dissolve any organic matter it finds on its way and deposit mineral matter and all the minute cavities left until they are filled and the porous mud or sand becomes solid in permeable rock fossils then preserved in this manner constitute the record of the history of life on the earth it is an incomplete record long periods of time are unrepresented because the sediments then deposited have been washed away or deeply buried or the fossils in them destroyed by crystallization a large proportion of the past life of this planet is imperfectly recorded or altogether lost because the animals had no hard parts to be preserved the vast majority of the records are undiscovered or inaccessible because they are still buried far beneath the surface and moreover the interpretation of the records is often doubtful yet the importance of paleontology or the study of fossil remains is great and it's teaching positive because the evidence is direct no one today would venture to question that the fossils of the rocks are the actual remains of animals which lived and died in former ages and the scientists knowledge of existing animals and plants is now complete enough for him to be able to declare positively that the animals which formerly inhabited the world were different from those of today and that in proportion as researches pushed backward in time the earlier forms were more and more diverse from their modern successors furthermore it is seen that the lowest and simplest groups of animals were of the earliest introduction to the past life of the world and that the higher groups have successively appeared in order of their complication and specialization in physical and mental structure throughout the geological record there is evidence of anecton or intermediate types linking together groups of animals now widely separated and the earliest appearing members of each group are more or less generalized that is to say their bodily structure conforms to the general type of the whole group but shows a combination of characters which are now found scattered among the various modern members of the group but seldom or never all combined in one animal these generalized characters also are apt to be anecton and link the group to other groups for example the birds and reptiles are now wide apart the birds being toothless feathered adapted to fly walking or hopping when on the ground and with the tail exclusive of feathers reduced to a little rudimentary stub while the reptiles possess teeth and scales and are crawling or swimming with long vertebrated tails but all the earliest birds had true teeth like reptiles and the oldest of them the archaeopteryx a long vertebrated tail feathered on the sides like the head of an arrow and on the reptilian side are found the dinosaurs among the more ancient reptiles resembling birds in many details of their bony structure and especially in their long legs adapted to walking instead of crawling and the pterodactyls a group of flying reptiles the latest of them tailless and toothless with horny beaks like the birds again there is a great gap among modern animals between fishes and four-footed animals of the land but the most ancient fishes are precisely those which come nearest in structure to the higher vertebrates and from which these might most readily have been derived through all the invertebrate groups the same conditions appear thus in a broad way the discoveries of paleontology tend continually to break down the sharp lines of distinction between the great modern groups and classes of animals and do so in just such a way as must follow if the doctrine of evolution be true if the various species, genera, orders and classes of animals are derived from a common ancestry through the evolutionary process it should be possible to trace the successive steps in the evolution and differentiation of each race by the fossil remains of its ancestral stages in the successive geological epochs this has been done precisely and in detail in many instances that it has not been done in all is due to the imperfection of the geological record to a peckable knowledge of it and especially to the vastness of the problem and the limitations in means, facilities or insight of those who are laboring to solve it broadly and approximately the course of the evolution of animal life has been traced out from the indirect evidence of structure and individual development and the more direct but less complete evidence of paleontology the task of working out and proving it in detail is as yet far from complete but among the thousands of workers who are devoting their lives to the study of fossils and their meaning not one has been led to deny the truth of evolution or to doubt the theory of descent difference of opinion among scientific men is as to the method not as to the fact closely allied to the nature of the animals of the past is the question of their habitat in early times involving the problem evoked by their present geographical distribution there are very few species of animals which inhabit more than a portion of the world most of them are limited to quite a small part of the land or water areas man is perhaps the most cosmopolitan of all land animals he inhabits every considerable land area of the globe except the Antarctic continent and a much smaller area around the North Pole most animals however are limited in their distribution by uncongenial climate or by barriers the species has not found means of crossing with land animals these barriers may be broad stretches of ocean extensive deserts high mountain ranges or great rivers with sea animals they may be continental barriers uncongenial stretches of coast and sometimes the volumes of fresh water poured out by great rivers but the limitations imposed by climate and temperature are the most efficient barriers to the worldwide distribution of either land or sea animals animals are dependent directly or indirectly upon plants for their food and the abundance and rapid growth of vegetation in the tropics affords opportunity for a corresponding development of animal life the profusion and variety of life in the tropics cannot fail to impress an observer from the temperate zone the struggle for existence everywhere going on is perhaps somewhat different in character it is an internecine war a strife for survival among the animals themselves rather than a combat against an unpropitious climatic environment in the temperate and especially in the arctic regions the element of struggle against the untoward conditions of outside nature is super added to the ever present war against other animals which scattered over a wider space is less apt to impress the observer although its influence on the development of the race may be no less powerful here perhaps in the double struggle against animals and against nature itself lies the reason for the dominance of temperate and northern types when brought into competition with the more abundant but less severely selected races of the tropics this fact is familiar in the case of man but it is equally true among animals the tropic regions with their abundant food and easy life are the refuge of inferior races succumbing and driven forth before the sterner competition of the north the zoological realms and provinces of the world correspond broadly with the geographic divisions and even to some extent with the political divisions since geographic and climatic barriers have conditioned the distribution of the races of men and thus largely influenced their governments in the land fauna it is observed that the great land mass of the northern continents forms one great zoological realm the holarctic South America a second the neotropical Africa south of the Sahara a third the Ethiopian and Australia a fourth the most isolated of all the various islands partake more or less of the character of the mainland adjoining but there are market differences which point to a different distribution of land and water in former times than now thus the animals of the British islands are almost identical with those of continental Europe while the animals of Madagascar are widely different from those of Africa the simplest explanation obviously is that the former have been connected with the mainland of Europe since the present species of animals came into existence the latter has been separated from the mainland since remote ages geological considerations support this view the marine provinces corresponded in part with the great oceans but are more influenced by zones of temperature than those of the land so far as shore animals are concerned their lines of distribution will be along the coastlines and a broad area of deep sea is as much a barrier to most of them as is a land barrier like the land animals however they give convincing evidence of former differences in the distribution of land and water there is a considerable proportion for instance of identical species on the two sides of the isthmus of Panama not found on the Asiatic or European coast hence there must have been communication between Atlantic and Pacific oceans either at the isthmus of Panama or elsewhere since these species came into existence they could not have gone around the horn because they are tropical species and are not found on the shores of temperate South America the geographic distribution of animals present and past together with the geological record of the evolution of each race furnishes a most important line of evidence on the past history and geography of the globe and under the name paleogeography a branch of study is being built up which is of great scientific importance as well as of transcendent interest its scope and vastness of purview are readily recognized when it is remembered that an intimate knowledge of zoology and of geology each of them vast and comprehensive is a prerequisite especially is this true of the lower orders of life which despite their simplicity afford the most fascinating realms of investigation and of section 2 recording by Melanie Young section 3 of the science history of the universe volume 6 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Lucy Park the science history of the universe volume 6 edited by Francis Schroed Wheeler zoology chapter 3 the lower invertebrates from the earliest times when sponges were believed to be but solidification of the foam of the sea they have been an element of curiosity to men they have been declared to be animal to be vegetable and to be mineral ancient naturalists quarreled over the question whether they could move or no and Aristotle's decision that they were animal because they shrank when moved from their rock bases provoked a storm of descent even so keen an observer as Lomarch believed the uppertures on the surface of a sponge to be the mounts of small cells inhabited by polyps and he expended no little wonder over the question why a polyp never was to be found in his cell Pasonel on the other hand declared that sponges were created by a giant sea worm and held that the sponge itself was mere nidus and excretion it is now known however that the ordinary sponge of bathtub importance is the horny skeleton of one of the simplest kinds of animals in life this horny framework is lined with an inner and outer layer of cells it is fast to a rock or coral block its movements consist only in inducing a current of water through the pores by means of tiny wet lashes attached to inner cells and by a certain amount of contraction and expansion of the entrances to the pores the cells absorb and digest any food matter that is brought by the currents of water passing through the pores most of the growth is by budding bisexual reproduction does occur however alternately with the giving off of gemmules or independent buds these gemmules produced in the autumn develop into male and female forms and the ova from the one fertilized by spermatoza from the other give rise to a summer generation of sponges which in turn produced gemmules this alternation of generations is now uncommon among lower animals there is a great variety of sponges some with calcareous skeleton others with horny or salacious skeletons they are nearly all marine and the best known kinds are tropical the commercial sponges of which the best come from the Mediterranean and Indian seas are found in clear water at moderate depths the fishermen locate them by looking through a glass bottomed bucket and pull them up with a pair of hooks on the end of a long pole they are left upon the shore to die and decompose and then washed and bleached among the salacious sponges some like the venus flower basket are exquisitely beautiful in the form and structure of the skeleton these live at great depths and are obtained by dredging fossil sponges are found in the most ancient rocks Professor Caillou has discovered the spicules of salacious sponges in the Archaean rocks of Brittany which would make them the oldest fossils known and they are common in the oldest facility of ferrous formations of other parts of the world so that the testimony of the rocks appears to confirm what would be expected that the sponges are the most ancient as they are the simplest of the methozoa or many celled organisms the corals and sea anemones, hydroids and jellyfish grouped under an order slantorata are but little less simple in form in all these animals the structure consists simply of a body cavity with a fringe of tentacles around the edge the tentacles are stinging and sensitive cells which serve to capture food the body cavity is lined with digestive cells which serve to digest it and is sometimes partially divided up by partitions extending inward from the outer wall and the outer layer of cells may secrete a cultureous shell which serves as protection the jellyfish are free swimming organisms the hydroids and sea anemones are fixed to the bottom the corals are great colonies of individuals which secrete a cultureous shell the translucent milky umbrella like disc of the jellyfish lazily opening and closing as it floats along the tide is familiar to everyone beneath the disc hangs a circle of long tentacles stinging cells which serve to kill or paralyze small fishes or other minute animals that may come in contact with them and are fluted into the body cavity by a current of water produced by the lashing of cilia or weep cells in the same way as in sponges many jellyfish can inflict a sting sufficient to cause severe pain to the incautious hand which touches them the structure of the stinging tentacles is very curious AG mayor in a seizure life describes them as follows the long flexible tentacles arise from the side of the bell near the rim the tentacles are covered with wart-like clusters of minute-thread cells each containing a coil tube which can be turned inside out as you might do with a finger of a glove if the tentacles come in contact with a small fish or crustacean these little stinging threads are instantly discharged and on account of their minute size they penetrate the skin of the prey carrying with them a poison believed to be forming acid which quickly paralyzes the victim the jellyfish produces eggs which however do not develop directly into free-swimming jellyfish but into fixed hydroids and these in turn bud off jellyfish this is another example of alternate generations hydroids differ from jellyfish in being fixed to bottom they are like little vases the lip line with stinging tentacles and many of them develop by budding into compound colonies many of the jellyfish are strongly phosphorescent at night and swarms of them floating in the water make a very brilliant display when stirred up by a boat passing through or by the breaking of waves upon the shore it may seem strange that such an animal as a jellyfish should leave any traces of its presence in the rocks nevertheless under certain favorable circumstances they may be buried in the sand and converted into silica casts without much loss of shape and these fossil casts known as star cobbles are found in the most ancient rocks of the Cambrian period in Alabama and elsewhere so it appears that jellyfish were among the inhabitants of the seas at the dawn of recorded geological history a sea anemone, says mayor, is a barrel shaped animal the bottom of the barrel is fastened to some rock or other firm anchorage while the upper end bears a slit like mouth which is encircled by a fringe of tentacles the mouth leads into a simple tube like throat which is bound to the inner size of the barrel by means of radiating partitions the throat tube is however only about one half as long as the height of the barrel so that the radial partitions in the lower half of the barrel cavity do not meet at the center but leave an open space which is the stomach of the anemone sea anemones are among the most attractive of marine animals beautiful both in form and color they vary in size from that of a pin's head to several feet across and they live at all depths and in a great variety of situations a coral polyp is only a sea anemone which deposits a plate of lime salts at the base of its barrel-like body and between the radial partitions of the stomach cavity these lime salts form a stony skeleton or substance which we commonly call coral it is well to remember that the coral animals are not insects but are merely sea anemones which form stony skeletons although sea anemones and coral polyps resemble beautiful flowers when fully expended they quickly contract into a mere dome-shaped mess when disturbed in this way the coral polyps are protected by withdrawing into their stony cup-shaped bases the coral polyps are glassy white and translucent and have each from 18 to 24 long tapering tentacles which end in a white knob and are speckled over with white warts these are the stinging organs which enable the coral to capture its prey of small marine animals when fully expended the polyps are about 1 eighth of an inch wide and 3 eighths high but when disturbed they suddenly contract so as to become practically invisible the colony starts with a single polyp but soon others bud out from its base and the cluster increases by further budding from the bases of the older polyps until it may be several inches in diameter the fleshy coral is found from the eastern end of Long Island to the Gulf of St. Lawrence it is rarely seen in shallow water but is common upon rocks at depths greater than 20 feet when first brought up from the bottom it appears as an ugly tough gelatinous mess covered with dull yellowish-pink finger-shaped processes if placed in water however the whole mess soon appears studded with beautiful star-shaped polyps which expended so as to give the appearance of a stump covered with delicate pink flowers each of these polyps has a terminal mouth surrounded by eight tentacles the sides of which are bordered with rays giving a feathery appearance the whole colony of polyps develops through constant budding from the sides and bases of the older parts of the colony nothing is more strangely beautiful than these coral reefs where the rich purple sea fans and the chocolate sea whips wave gracefully to the surges in the crystal depths while brilliant fishes glistening in green blue purple and yellow glide in and out among the shadows of the coral caverns the precious coral of the Mediterranean is allied to the sea whips its polyps are brilliant white and have each eight feathered tentacles while the internal axis of the colony is red and stony the stony corals especially the reef-building kinds have played an important part in the building up of the continents they flourish in a warm temperature and clear water in the west Indies the Red Sea and Indian Ocean the northeast coast of Australia and especially in the islands of the Pacific coral reefs today are building out the land on a gigantic scale and their influence has been even more important at times in the past history of the earth the lower part of the peninsula of Florida consists of a succession of reefs built out one after another the latest being the Florida Keys the outer border of the reef is alive and growing the fragments broken off by the waves from above filling up the interceases between the growing corals and slowly extending the bank seaward the lime extracted by the little coral polyps from the sea water and built up into solid limestone reefs would in the course of time exhaust the entire supply of lime salts in the ocean where it not continually recruited by the lime dissolved from limestones on land by the rain or liberated in the decay of other rocks this lime is brought down by the rivers in the form of a soluble bicarbonate and in extracting it from the sea water the corals and other lime secreting organisms set free a certain amount of carbonic acid gas which again is not without effect upon the climate starfish sea urchins sea lilies and sea cucumbers forming the order of Aquino Dermata, Cessmayr are also called radiates because in the form of their bodies and arrangement of their organs they usually display 5 rays for example, most starfishes have 5 equally developed arms 72 degrees apart recalling the rays of a conventional star in the Aquino Derms the skin usually contains a skeleton composed of cautious plates of definite shapes all hinged together in an orderly manner so as to make a vertebral armor which gives rigidity to the body and protects the soft organs of the interior in the living starfish one will see hundreds of little tubular feet which arise from the grooves on the lower side of the arms when the starfish is turned over upon its back these feet stretch out to a remarkable length and wave about seeking to fasten upon something in order to ride the animal it is then we may see that each of these feet is a hollow tube ending in a cup shaped sucker similar tube feet will be seen in 5 double lines along the sides of the sea urchins the mouth of the starfish is at the center of the lower surface on the upper side and a little away from the center between two arms one will see a spongy looking area this is called the metroporic plate and is the sea-like entrance to the water tubes of the starfish which extend down the arms and give rise to little bladder-like vessels one above each tube foot the contractions of these little bladders cause the tube feet to elongate by pressing water out into their cavities the upper surfaces of most of the starfishes are covered with its spines but these are much better developed in the sea urchins where in addition to spines are found cautious pincers mounted upon rods which are used to remove any injuries foreign substance that may fall upon the body of the urchins the sea cucumbers or holothuria are worm-like in appearance but are never exclusively related to starfishes and sea urchins they have no spines and their skeleton is often reduced to minute anchor shaped spicules within the skin the mouth is at one end of the worm shaped body and is surrounded by feathered or branching tentacles in some species there are five double rows of tube feet down the sides of the body but in others these are absent when disturbed sea cucumbers have the curious habit of casting out their viscera and after regenerating them they are sluggish creatures and either live within the sand or under rocks or cross slowly over the bottom feeding upon minute organisms that are contained in the sand or mud which they swallow sea urchins or a kind may be compared to starfishes without arms they are usually provided with a skeleton made for the most part of six sided plates fused or rigidly joined together they have five sharp edged teeth with which they gnaw off minute seaweeds from the rocks some species can even gnaw away the rock itself and in many parts of the world the sea urchins have literally honeycombed the rocks indeed a sea urchin is often found living in a cavity whose opening is too small to allow of the animals escape the common sea urchin of Europe is sold in the markets during the season when it is full of eggs the sea lilies or crenoidia may be compared to a starfish mounted upon a long stem which arises from the middle of its back and anchors it to the bottom of the sea the mouth is turned upward and is surrounded by branching arms which sweep gracefully to and fro in search of prey the achinoderms live only in salt water but they are found at all depths and in all oceans from the tropics to the poles the vast majority crawl over the bottom but at least one Holothorian swims through the water and was at first mistaken for a jellyfish most of them cast their eggs out into the water and the larvae develop bands of swimming cilia which enable them to swim about for a considerable time suddenly the body of the achinoderm begins to develop with the larva most of the old larva body is absorbed or cast off starfishes feed upon almost any kind of mollusk but will also devour barnacles, worms and occasionally sea urchins or even the young of their own species it is estimated that in one year starfishes destroyed 631,500 dollars worth of oysters on the beds of Connecticut alone in the mode of feeding the starfish folds its arms over the clam or oyster and hundreds of the sucker like tube feet fasten themselves to the valves of the shell so that finally the mollusk yields to the constant pull of the starfish and the shell gapes open then the starfish turns its stomach inside out and engulfs the mollusk it has been found by experiment that a large starfish can exert a steady pull of over 2 and 1 half pounds and that this is sufficient in time to open the valves of the clam or mussel the eggs of the starfish are discharged into the water in greatest abundance during the last 3 weeks of June although they are also to be found throughout the summer and occasionally even in winter these eggs are soon developed into little transparent larvae covered with torturous lines of waving cilia and provided with long flexible tubercles they swim slowly about near the surface and feed upon minute organisms until they grow to be about 1 eighth of an inch long then the upper and lower halves of the star begin to develop upon each side of the stomach and in a few hours all of the anterior part of the larva and the tubercles are absorbed then a minute star about as large as a pin's head is seen upon the bottom of the ocean myriads of these little stars settle upon seaweeds and eelgrass and begin at once to devour the young clams which also begin life in the same places Professor Mead found that one of these little stars devoured over 50 young clams in 6 days the starfishes grow rapidly and in one year they may have arms 2 and a half inches long and be ready to spawn besides the common 5-pointed starfish there are many other more or less familiar the serpent stars have long slender flexible arms and are much more active in the basket stars the arms are branched and forked into a multitude of slender interlaced tips upon which the animal moves about with the body lifted above the ground the prickly sea urchins abound along rocky coasts along the sandy shores they are replaced by the sand dollar flattened out into a thin plate covered with minute brown spines sea cucumbers are familiar to everyone who has explored the tide pools of rocky coasts at low water but other kinds are common on sandy muddy or gravelly beaches living just below low water mark in China a species of sea cucumber is prepared and eaten as a delicacy sea lilies or crinoids are now rare and confined to deep water but in the early periods of geologic time they were very abundant and varied shore forms as well as deep water species the oldest of them dating back to Cambrian period suggest a sea urchin which has lost its spines and is mounted upon a jointed stock in the crinoids proper the body has developed branching arms which wave in a feathery plume above it the fossil crinoids or stone lilies are sometimes preserved in wonderful perfection in the paleozoic limestones and are one of the most attractive of fossils great numbers of them have been obtained in the limestones of Crossfordsville, Indiana and elsewhere in the United States End of Section 3 Recording by Lucy Park Section 4 of The Science History of the Universe Volume 6 This is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org Recording by Lucy Park The Science History of the Universe Volume 6 Edited by Francis Roald Wheeler Zoology Chapter 3 The Lower Invertebrates Part 2 The title Worms says Professor Thompson is hardly justifiable except as a convenient name for a shape The animals to which the name is applied form a heterogeneous mob including about a dozen classes whose relationships are imperfectly known but the zoological interest of the diverse types of worms is great for amid the diversity we discern affinities with cilantro, akinoderms anthropodes, mollusks and vertebrates Moreover it is likely that certain worms were the first to abandon the more primitive radial symmetry and moving with one part of the body always in front to acquire head and sides and if one end of the body constantly experienced the first impressions of external objects it seems plausible that sensitive and nervous cells would be most developed in that much stimulated overeducated head region but a brain arises from the in-syncing of ectodermic skin cells and it's beginning in the cerebral ganglion of the simplest worms thus in part explained Most of the creatures which fall into this group are of little interest to the general reader Many of them are parasitic some, like tapeworms, threadworms, flukes and trichinae are implicitly familiar in this connection The simpler and segmented worms are those which most nearly represent the remote ancestors of mollusks and of vertebrates The higher segmented worms or analytes follow more definitely along the line of crustacean and insect evolution and them may be found an arrangement of organs and plan of bodily construction which serves to explain how the organization of the crustaceans and insects has been developed The common earthworm is most familiar of the analytes and its anatomy is much more interesting and complicated than might at first be supposed The surprise is great that awaits the man who first dissects an earthworm With proper cleaning and dissection he will be able to see a complex and wonderful structure a plan of organization wholly different from that of the higher animals, vertebrates yet subserving to a large extent the same purposes and beautifully adapted to the needs of the earthworm's life and habitation to figure out that delicate mechanism on the prongs of a fish hook is likely afterward to appear to him a sort of disregard of proportions much like throwing a gold watch at a stray cat Of the anatomy a detailed account cannot be given here It must suffice to say that it has a straight elementary canal stretching from the mouth at the front end to near the hindered end of the body The front end of the canal being provided with a muscular ring and with glands which aid in swallowing and digesting the earth which forms its food There is a circulatory system consisting of a slender tube along the midline of the back and others along the underside joined by several cross veins encircling the throat which by expanding and contracting enable the colorless blood to circulate through the body It possesses also a nervous system consisting of a cord corresponding to the spinal cord of higher animals but situated on the underside of the body along the midline and double instead of single with little not light expansions or ganglia at every segment which correspond to the brain of the higher animals and with a separate pair of ganglia on the dorsal, upper side of the head united with the front pair of ganglia of the underside by a pair of cords encircling the gullet There are no eyes or other specialized sense organs or special organs of respiration yet the worm is aware of the approach of enemies or of light and darkness through a general sensitiveness of the skin and the blood is aerated through the skin There are however the beginnings of organs of excretion to remove waste matter from the circulation and the reproductive system is quite elaborate the animal being hermaphrodite that is combining both sexes in one individual but so arranged that the eggs of one earthworm must be fertilized by another The chief economic importance of earthworms is as principal agents informing the mantle of humus or soil which covers the dry land in all parts of the world and buries the hard rocks and sterile soil beneath it Earthworms abound in all parts of the world they eat their way through the soil and come out at night to the surface where they forage around for leaves and stray bits of vegetable matter which they drag to their burrows to be nibbled and swallowed at leisure Their castings composed of the earth and community vegetable matter which they have swallowed and digested are deposited on the surface and in the course of their lives they bring up a good deal of the sterile under soil mix it thoroughly with particles of vegetation from the surface and deposited in their castings These accumulating year after year and century after century form the layer of humus or topsoil in which vegetation chiefly thrives and on which the gardener and farmer depend for the successful growth of their crops Not all the humus is due to earthworms Insect larvae plays some part and to a large extent it is merely due to natural decay of surface vegetation and its mixture with soil by rain and the dust brought by the winds but the investigations of Darwin show that the earthworm plays an important part in its formation thus as the tiny coral polyp is ever helping to form the continents on which man can live and perhaps also to control the climate and moderate the extremes of temperature so also the earthworm is rendering efficient aid in covering the land with rich and fertile soil enabling vegetation to flourish and making the earth habitable for the human species The name mollusks or soft-bodied animals covers an immense number and variety of invertebrates the clams, oysters and other shellfish, the snails and slugs, the octopus and squid and many less familiar types All of them have soft bodies, usually with an external cautious shell but with no internal skeleton except in the squids and their relatives They are much more highly organized in the coral or starfish groups The arrangement of the organs shows a bilateral symmetry unlike the radial symmetry of coral or starfish that is to say the organs and parts of the body are arranged in pairs on each side of the middle line so that there is a front and a hindre end of the body On the other hand, the body is not divided into successive segments as in the worms, crustaceans and insects Most of the mollusks are sluggish animals many of them attached to stones or other objects on the bottom but the squid and condo fish are swift and active The lower surface of the body, cesmire, consists of a thick muscular foot used in creeping In front of the foot is the head which may have a pair of vines and tentacles while the mouth lies on its lower surface and is often provided with numerous horny, rasping teeth A flap-like fold of the body extends outward from the sides This fold is called the mantle and its free edge and upper part secretes the shell which usually covers the back of the mollusk The feathery gills arise from the sides and lie in the space between the lower side of the mantle and the side of the body The intestine is coiled and opens typically at the posterior end of the body behind the foot There is a paired digestive gland or liver which pours its secretion into the mid-gut The three-chambered heart lies above the hind-gut and pumps blood from the gills to other parts of the body In addition, it may be noted that the mollusks show well-defined muscles and nervous system The latter consists of a number of ganglia, knots or nods of gray matter corresponding in function more or less the brain of higher animals connected by cords of nerve fibers which may be said to correspond roughly to the spinal cord in higher animals From these ganglia, nerves are given off to the various parts of the body This concentration of the nervous system into a few-defined ganglia connected by cords is a great advance upon the condition in the lower invertebrates where the nerve cells are diffused and scattered over the surface of the body It makes possible a much more exact and definite correlation of the movements and actions of different parts of the body It is like the establishment of a central executive bureau to control and order the activities of some great and complex organization The great majority of mollusks are marine, chiefly short-living although some are adapted to deep-sea life But many inhabit freshwater lakes, rivers and streams, and one group, the landsnails, has become adapted for terrestrial life, breeding air instead of water The principal groups of mollusks are 1. the bivalves or lamella branchs comprising clams, oysters, mussels and other shellfish in which the shell consists of two valves, right and left 2. snail shells or gastropods including snails, welks, periwinkles, limpets and others in which there is a single valve, mostly spirally coiled The symmetry of the animal is obscured in this group by development of one side and the slugs the shell has degenerated to a small horny scale buried in the body 3. squids and cuttlefish or cephalopods including also the octopus, nautilus and a host of extinct forms They are free-swimming active animals with a ring of muscular tentacles around the mouth and part of the foot, modified into a funnel The siphon, through which water can be forcibly expelled from the mantle cavity, driving the animal backward These are considered the highest development of molluskian life and account of their active habits and more concentrated nervous system The lamella branchs feed upon minute organisms, both animal and vegetable which they sift out from the sea water by the aid of gills The gastropods are more generally carnivorous, feeding upon other mollusks which they attack by boring a hole in the shell by means of a ribbon-like tongue, the radula armed with many small, sharp, horny, rasping teeth and then sucking out the juices of their victims This unique little implement appears to be very efficient for its purpose and is said to be aided by a secretion of sulfuric acid Other gastropods, such as the periuncles and the freshwater and land snails, feed upon plants but all of them possess the radula The cephalopods also are carnivorous, the octopus lying in wait for unwary fish or crustaceans which may come within reach of the long tentacles The squids capturing their prey by darting rapidly backward, swimming quickly to one side and seizing the victim in their sucker-bearing arms The molluskia include an immense number and diversity of animals In the gastropoda alone, there are over 15,000 living species The lamella branchs are hardly less numerous Many of them are edible, a few are important articles of food The oyster fisheries in the United States alone are estimated to yield 16,600,000 U.S. dollars annually The soft shell clam of the North Atlantic, the scallop and the round clam or cohog of the Middle Atlantic States are important articles of commerce, while mussels, welks, periuncles and land snails also are largely eaten in Europe The pearl oysters of the Indian and Pacific Oceans and the freshwater pearl clams of the United States are likewise of importance not only for the pearls but for the much larger industry in mother of pearl obtained from the shells and manufactured into buttons and pearl ornaments The pearl fisheries in the Persian Gulf alone are said to be worth 2,000,000 U.S. dollars annually The noxious activities of mollusks are slight A few species commit depredations upon oyster beds The damage done by the pterodose to timber underwater is more serious The gruesome tales of attacks upon men by the devilfish or octopus are mostly fanciful An octopus, if large enough, no doubt could and would attack a man if he came within reach and once in a while he might catch him at a sufficient disadvantage to overcome and destroy him But chances for such an encounter with such a result are exceedingly small Members of this group of mollusks do not attain a gigantic size, however These huge forms are deep water organisms and are very rarely seen by men although they form an important part of the food of marine animals such as the seals and sperm whales During the whole recorded geologic time, mollusks have been an important element in the marine fauna Freshwater mollusks are probably equally ancient and land mollusks are known to have appeared as far back as the coal era Their hard and destructible shells are the most abundant of fossils, often making up the entire mass of limestone strata Tamela branks, gastropodes, and cephalopods were all distinct as early as the Tamburian period Their evolution from a common stock must date far back into the unrecorded beginnings of geologic time The shell cephalopods related to the modern Nautilus attained great size and abundance early in geologic time and were then the dominant type of marine life In Orthocerus, the shell is sometimes seven feet long, straight instead of coiled as in the Nautilus During the age of reptiles, the cephalopods were again very abundant marine forms Nautilus, Baculites, etc. coiled, partly coiled, or uncoiled, being probably more nearly related to the Squid and Octopus than to the Nautilus But the majority of fossil shells are related to the modern Lemp shells and their allies The brachyopoda, which although mollusks like, are not true mollusks The plan of organization of the animal being wholly different The shell may be distinguished by the fact that its valves are dorsal and ventral instead of right and left with respect to the symmetry of the animal These brachyopoda are considered a class apart or grouped with bryozoans into the molluscoidea Their relations are about as close with worms as with mollusks, but not very near to either The living brachyopods are rare deep water organisms crowded out from shallow water by competition of the more highly organized mollusks But in early geologic times, they were the common shells of the seashore With the crustaceans begins the Anthropod series of invertebrates, characterized by a segmented body, jointed limbs, and an outside skeleton The name Anthropoda, jointed feet, points to the distinction that separates them from the worms But their plan of organization is evidently derived from that of the segmented worms or anelids The crustaceans are adapted to aquatic life and breed by gills The insects are adapted to terrestrial life and breed by trachea The spiders and their allies include both land and aquatic types, differing from either insect or crustacean in their plan of organization The lobster and crayfish are the most typical crustaceans, the first marine, the second living in fresh water In comparison with the worms, it is observable that while the body is segmented, the segments are not all alike But are divided into two regions, the head and thorax and the abdomen Likewise, the appendages are not mere bristles as in the worms but jointed and specialized to serve different purposes The most anterior ones, antennae and anteneals, are organs of touch and smell, enabling the lobster to feel his way about Next comes six pairs which serve chiefly to aid in biting and chewing the food Then the large forceps to seize the prey, then four pairs which are used in walking and six posterior pairs used mainly for swimming purposes Altogether, there are 19 pairs of appendages The stocked eyes are not classed as appendages, being of different origin The segments and appendages are enveloped in a tough horny covering, flexible at the joints, hardened elsewhere by lime solids and rigid armor The internal organs of the lobster are much more elaborate than in the worm, but their general plan is much the same The nervous system is more concentrated, the muscles are distinct and well developed The alimentary system consists of first a gizzard with a complex mill for grinding up the food Then a mint gut stomach with a large digestive gland which takes a place of liver, pancreas and impart the stomach glands of higher animals And finally a long straight hind gut which takes with small part in the digestive process The colorless blood enters the heart from the gills through the valves which admit of entrance but not of exit Then it is pumped through well-defined arteries to the tissues of the body from which it returns through ill-defined channels to the gills The gills are feathery structures of a rather complex nature, presenting a large surface to the current of water which the animal keeps going through them by paddling with part of the fifth pair of appendages There is also a distinct excretory system, kidney, and the reproductive organs are more elaborated than in the worm, the sexes being separate And it's thus a much higher type of animal than the earthworm but the plan of organization is the same as it is also in the insect The mollusk and vertebrae are organized upon entirely different plans The lobster occasionally attains great size and one specimen, 3 feet and 6 inches long and 30 pounds in weight was captured off the New Jersey coast in March 1897 The snapping prawns are little lobster-like crustaceans of the American coast The largest are not more than one and three quarters inches long One claw is much larger than the other and is provided with a sharp edged blade which is normally held out at right angles to the claw At the least alarm this blade is closed with a sharp snap, reminding one of the explosion of a small torpedo These little creatures live in crevices of coral reefs under shells and stones and fairly swarm in sponges So that when a sponge is lifted from the water, it crackles as if filled with minute firecrackers The shrimps are similar in many ways but are free swimmers A crab is essentially a lobster with its tail turned in under its body It is the highest of the crustacea and the species is widely distributed and varied Extending from the combative edible or blue crab to the parasitic hermit crab Ranging in size from the tiny oyster crabs which live with the gill cavity of the oyster To the giant spider crab of Japan which attains a span of 12 feet Including deep sea crabs which never come to the surface and the land crabs of the tropics which rarely enter the water And which, like the robber crabs, climb trees and live on coconuts Barnacles, while mollusk-like in appearance, are rarely crustaceans which have affixed themselves to rocks or floating objects And are enclosed in a hinged, luxurious shell As Huxley put it, they are fast to a rock by their heads and kick the food into their mouths The stock barnacle, or goose barnacle, was believed by writers of the Middle Ages to undergo a metamorphosis into a species of goose The barnacle goose, and this transformation was repeatedly asserted in the most positive terms down to the time of Linnaeus or even later Being encased in a natural armor says mayor in sea shore life Crustaceans cannot grow at a uniform rate but enlarge suddenly at the periods when the shell is shed This occurs at fairly regular intervals and the entire shell is shed, even the coverings of the eyes and part of the lining of the stomach being cast off The creature is then soft and helpless and usually remains hidden in some safe retreat until the body has expended and the new shell hardened Owing to their hard outer armor and their aquatic life, remains of crustaceans are very common as fossils and there is a fairly complete record of their evolution The higher types, such as crabs and lobsters, did not appear until after the coal period But the more primitive, mostly minute crustaceans known as ostracods and filipods have been traced as far back as the Cambrian, nearly to the beginning of recorded geological history The trilobites, familiar to every geologist, were a primitive group of crustaceans which flourished during the older geologic periods, becoming extinct in the coal period They are very abundant and characteristic fossils and palozoic strata, many of them attained considerable size, the largest up to 2 feet in length End of section 4, recording by Lucy Park