Invertebrate

“ A volume would not suffice to enumerate the invertebrate or insect-like life that lived in this dark passage-way beneath the sod; nor do we wonder at finding such low forms groping in utter darkness; but why higher animals that are found, and far more frequently, in the open air and sunlit waters should delight to crowd these same gloomy quarters, is a problem not so easily solved. ”

“ Most animals appear first as eggs laid by the mother. This is true of the birds, the reptiles, the fishes, the insects, and most of the hosts of invertebrate animals. This egg may be cared for by the parent as with the birds, or simply deposited in a safe place as with most insects, or perhaps dropped without care into the water as with most marine invertebrates. ”

“ Birds, mammals, reptiles, fishes, and invertebrates may each be detected in earlier strata; even in some of those formations now regarded as non-fossiliferous, organisms may be found; but it is not at all probable that the preponderance of reptiles will ever cease to be the essential characteristic of the Secondary rocks, or that of mammals of the Tertiary, or that a preceding period of vast duration, in which the type of life had been the invertebrate, will ever be doubted. ”

“ We here enter upon a marvellous field of discovery. Hitherto the forms of life we have met with have all been invertebrate. The trilobite, something between a crab and a beetle, once revelling, in untold myriads, probably on the land as well as in the water, and of which two hundred and fifty species have been brought to light, is the highest type of life with which our researches have made us familiar. We are 69now to begin the study of fossil fish, and to their discovery, strange forms, and characters, this chapter will be specially devoted. ”

“ In this connection, it is interesting to observe that creatures endowed with the highest intelligence, both vertebrate and invertebrate, manage to survive in considerable numbers in regions devoid of water. ”

“ From the time of its appearance, this work has ever been regarded as one of the highest authority, and has formed the principal regulator of most departments of this extensive race of animals. The work extends to seven octavo volumes, and is entitled “Natural History of invertebrate Animals, presenting the general and particular Characters of these Animals, their Distribution, Classes, Families, Genera, and the principal Species referable thereto.” ”

“ Although all the chief groups of invertebrates are represented in the abyssal fauna, their relative proportions are unequal; molluscs, crabs and annelids being, as a rule, scarce, while echinoderms and sponges predominate. (5) Depths below 500 fathoms are inhabited by a practically uniform fauna, the genera being usually cosmopolitan, although the species may differ, and be represented by allied forms in widely sundered areas. (6) The abyssal fauna, so far as invertebrates are concerned, is of an archaic type as compared with shallow-water faunas. ”

“ The marine fauna is always large and varied, comprising, typically, representatives from each taxonomic division among the invertebrates. Not only are there a large number of genera and species, but nearly all phyla are represented. For the mollusca alone the number of genera in a given region may run up into the hundreds and that of the species may be considerably over a thousand. ”

“ In the sea, the tropical plains with their tangled vegetation and plentiful animal life are represented by the still more uniform plain forming the submerged continental 13 shelf with its strange forests of flowerless plants, the seaweeds. These submarine jungles shelter hosts of animal species, many of which swarm in countless myriads. This life embraces all grades of invertebrates, such as the microscopic protozoa, sponges, radiate animals like the coral-polyps, starfishes, sea-urchins, etc., and crustaceans in vast variety, and, among vertebrates, includes fishes, reptiles, and mammals. ”

“ The faunas of the more ancient formations he holds to be far less imperfect than has been often supposed, where the vertebrate type is represented by the fishes, and whose structure is as complicated and finished as the most recent of their kind; while the invertebrate again furnishes numerous examples of fossilized gasteropoda and cephalopoda, the most perfect orders of the molluscous class. ”

“ Sir John Murray says fishes and members of all the invertebrate groups are distributed over the floor of the ocean at all depths. The majority of these deep-sea animals live by eating the mud, clay, or ooze, or by catching the minute particles of organic matter which fall from the surface. ”

“ So in our descent from the surface on which men live, through the successive rocky layers of the earth's crust, we leave behind, one by one, all the higher forms of life with which we are familiar; but there still remain to us our six groups of aquatic invertebrates, in the guise, it is true, of species and genera now unknown in a living state, yet well represented as far down as the lower part of the Cambrian. ”

“ Slender as our knowledge is of the earlier evolution of the Invertebrate animals, we return to our Cambrian population with greater interest. The uncouth Trilobite and its livelier cousins, the sluggish, skulking Brachiopod and Mollusc, the squirming Annelids, and the plant-like Cystids, Corals, and Sponges are the outcome of millions of years of struggle. ”

“ Dividing the vertebrate animals—as Linnæus had already divided them—into mammals, birds, reptiles, and fishes, he divided the invertebrates into molluscs, insects, worms, echinoderms, and polyps. In 1799 he separated the crustacea from the insects, with which they had been classed hitherto; in 1800 he established the arachnids as a class distinct from the insects ”

“ Because of their connection with our industries or our food supply, some of the Invertebrates are familiar [440] to all; for instance, sponges, corals, starfishes, crabs, shrimps, lobsters, clams, and oysters. Others are seldom seen unless one takes pains to look for them.
JELLY FISH
All life comes from pre-existing life. So every animal living to-day has come from some other living animal and every plant living to-day has come from some other previously living plant. It is believed that the first forms of life came from the water. ”

“ Many of the lower invertebrates choose special localities in which to deposit the ova or embryos, and glands, the viscid secretion of which serves to bind the ova together or to attach them to some external object, are frequently present. In many insects, elaborate preparations are made; special food-plants are selected, cocoons are woven, or, by means of the special organ known as the ovipositor, the eggs are inserted in the tissues of a living or dead host, or in other cases a supply of food is prepared and stored with the young larvae. ”

“ In the sea, whales, sharks, and teleost fishes of modern types rule in the stead of huge swimming reptiles. The lower vertebrates, the invertebrates of land and sea, and the plants of field and forest take on a modern aspect, and differ little more from those of to-day than the plants and animals of different countries now differ from one another. From the beginning of the Cenozoic era until now there is a steadily increasing number of species of animals and plants which have continued to exist to the present time. ”

“ From the point of view of the fauna as a whole, the zoological classification of the soil invertebrates is only significant when the various groups are analysed according to the feeding habits of their members. All animals are directly or indirectly dependent upon plant life for their nutrition. ”

“ The broadest general division of the Animal Kingdom is into back-boned animals (Vertebrates) and those which have no back-bone or equivalent structure (Invertebrates) . [1] The former includes, besides- 8 - man himself, the familiar groups of Beasts, Birds, Reptiles, and Fishes. The latter consists of the great swarms of creatures included under the terms Insects, Crustaceans, Worms, Cuttle-fishes, Snails, Bivalve Mollusks, Star-fishes, Sea-urchins, Coral Animals, Sea-jellies. Sponges, and Animalcules. This mixed multitude of animals, mostly of low grade and aquatic. ”

“ The fishes and reptiles have received some attention too; and, in the lower, invertebrate forms of life, the investigations of Thomas upon the grasshoppers, Carpenter on the butterflies and moths, and Edwards, Packard, and Hagen on other insects, and the reports upon Crustacea and worms by Verrill, Smith, Leidy and others, have given us a tolerable knowledge of the extent to which those forms are to be found in that region. But the mollusks of the mountains—land-snails, pond-snails, river-snails, and fresh-water mussels—have been almost entirely neglected, except by Dr. ”

“ But, in addition to these, fishes among Vertebrata are introduced, but fishes only, all of which are exclusively marine. At a somewhat later period insects come in. We find next reptiles in addition to fishes—the lower classes, or invertebrates, continuing to be represented through all subsequent epochs, but by species changing gradually at each period, as all classes do after they have been once introduced. ”

“ They then take up, more briefly, the relatives of the insects, the spiders and crustaceans, following these with the higher invertebrates, reaching the fish in April. This, for obvious reasons, is their last dissection. But with living material, and the beautiful preparations and stuffed specimens with which the laboratory is filled, they get a very general idea of the reptiles, birds, and mammals. This work is of necessity largely done by the students out of school hours. ”

“ Most invertebrates and many of the lowest two classes of backboned animals, the fishes and the amphibians, cannot merely stop up a rent, but renew an entire limb, fin,—yes, even eye or head. Cut an earthworm in two and the rear half will grow a new head and the front half a new tail. ”

“ Cope, not less than 150 species of vertebrate animals alone, of which 100 are new. This makes no account of the collections of the invertebrates. "There is a view generally entertained by naturalists and geologists, that genera and species of animals and plants are greatly more numerous at the present age of the world than in any previous geological period. ”

“ That the average person should be more conversant with the vertebrates than the invertebrates is, to a great extent, the natural outcome of association and training; a possible influence is to be found at the outset of one’s career in the many illustrated nursery books depicting game and domestic animals, but seldom, if ever, any of the invertebrates; and this impression tends to be further fostered in later life by visits to the zoo, where we meet in person most of the nursery book animals, and perhaps some of the lower forms, such as insects ”

“ Ornithology and entomology are the studies which now impel most field-work, and for actual observations the followers of the first science appear to almost excel those of the second, a conclusion hitherto scarcely suspected—at least by the writer.
There are many invertebrates which are practically ignored in our pages. ”

“ It was known that fishes formed a class of the animal kingdom distinct from mammals, birds, or invertebrates, long before it was recognised on the one hand that fishes might be bony or cartilaginous, or on the other that fishes, birds and mammals composed a group differing from the invertebrates by many common characters. ”

“ It is, however, among the higher invertebrates—especially among the insects, and of them pre-eminently in the social hymenoptera, ants and bees, that the most remarkable and complete instincts are seen. ”

“ In this brief study we shall not go into much detail about invertebrates, but with the backboned animals or vertebrates we shall go a little further. These may be divided into five general groups: (1) Fishes; (2) Amphibians, which include frogs, toads, and [379] salamanders; (3) Reptiles, which include alligators, crocodiles, turtles, lizards, and snakes; (4) Birds; (5) Mammals.
This simple analysis may be clearly shown by the following diagram ”

“ I have therefore selected a few of the largest and most conspicuous families, which have been so assiduously collected in every part of the globe, and so carefully studied at home, as to afford valuable materials for comparison with the vertebrate groups, when we have made due allowance for the dependence of many insects on peculiar forms of vegetation, and the facility with which many of them are transported either in the egg, larva, or perfect state, by winds, currents, and other less known means. ”

“ Some of its beds consist of a range of certain species possessing a considerable similarity; while in others, animals of the most opposite habits, and inhabiting different regions of the globe, as well as different elements of nature, are strangely brought into contact, and confusedly blended in one heterogeneous mass. Shell-fish of the rivers and of the sea, corals, fishes of various kinds, insects, bones of different species of birds, remains of elephants, bears, and other quadrupeds, requiring for their existence different climates, are here united in an extraordinary assemblage. ”

“ In the end the insects became, owing to this acquisition of wings, and afterwards to the establishment of a complicated metamorphosis, numerically the most successful type of life in existence, the number of species, extinct and living, mounting into the millions.
All aquatic insects are evidently the descendants of terrestrial forms, and the numberless contrivances and temporary larval organs, particularly of dipterous larvæ, are evidently adaptations to the needs of the insect during its aquatic life, and which are cast aside when the creature passes to a different medium. ”