Читать книгу Animals before man in North America - Frederic A. Lucas - Страница 7

Table of Contents

The history of modern times can not be taught without mentioning dates, or giving the names of nations or of men; nor can the history of the past be discussed without frequent reference to periods of time, groups of rocks, or animals, or even particular individuals among them.

So, at the outset, it will be necessary to say something of the principal divisions of animals, rocks, and time, and of the methods by which they are arranged or classified; for classification is merely setting things in order, placing together related objects, be they animals, plants, or rocks, just as we might arrange books in a library. We would hardly put books on the shelves just as they came to hand, nor would we place books of various kinds side by side, merely because they were bound alike. We would naturally group them according to their subjects—histories in one place, novels in another, books of travel in still another. And just as books are arranged by their subjects or contents, and not by their bindings, so animals are classified according to their contents or structure, and not by their coverings, form, or external appearance. If in the present brief review of the animal kingdom more attention seems to be paid to mere appearance than to those plans of structure by which animals are grouped, it is because to the great majority of people appearance is not only the more interesting but very much the more familiar. Very few care to trouble themselves with the plan on which a creature is built any more than they would care for the plans of a pretty cottage; the completed structure is the thing of interest. But the paleontologist, the delver into the ruins of the past, rarely has more than the framework to deal with, and counts himself as extremely fortunate if the greater part even of this be not missing. So the reader will please take it for granted that the various assemblages of animals mentioned are each characterized by some common peculiarity of the plan on which they are built; and if he doubts this he has only to refer to some good work on zoology. And if the name of a division of animals can be associated in the mind with the form of some one of its more familiar members, we can understand very well what is meant when the group is referred to.

Animals are, according to their degree of relationship, placed in larger or smaller assemblages, the principal of which, in the order of their size being known, beginning with the largest, as Classes, Orders, Families, and Genera. Letting books as a whole stand for the subkingdom Vertebrata, the classes may be said to roughly correspond to books of a given kind—histories for example—and the orders to those relating to the history of one country, while the families would be represented by histories of a given section of that country. As for genera, we will look upon them as books telling, as they often do, the story of a single town, or some particular event, and the species as those written by the various authors. And just as the events pertaining to the history of one small portion of a country might require many volumes for their proper record, while a single book might contain all that was to be said of another and much larger section, so one family of animals, or an order even, may comprise many genera and species, while another may contain but a single species. And one of the first things to be remembered is, that the rank or importance of any division does not depend on the number of species it contains, but on the extent to which these agree with or differ from the members of other groups.

Right here it may be well to forestall the complaint that is so often made, that animals are overburdened with long scientific names, and reply to the frequently asked question, Why is it that they have no popular names? The reply is simple; a common name can be used only where an object is common, and many living and most fossil animals are so little known as to have received no popular appellations. The scientific names given them appear strange and seem difficult only because they are unfamiliar, and are often much simpler than many of the so-called “common” names. How many readers know what a potto is, a colugo, mulligong, scheltopusic, cacomistle, or wobblygong? And yet these are popular (?) names. Then, too, these so-called “common” names may have different meanings in different places, so that woodcock may be a woodpecker or a species of snipe, and partridge may refer to a quail or a ruffed grouse, while the term pheasant applied to the latter in some portions of the United States is an utter misnomer, for no true pheasant is a native of America. The popular name, like the cowrie money of Africa, is good only for local use; the scientific name, like a gold coin, passes current in all civilized countries.

Scientific names, like those of persons, originated in the attempt to define an animal in a few words containing some allusion to its appearance or character. The names Smith, White, or Strong once described the individuals to whom they were applied, and this kind of name is in use among savages to-day. And as names have become changed by use, ceased to be descriptive, and used merely to designate the individuals to whom they are given, so scientific names have been cut down to two parts. The first of these is the generic name, and includes all closely related species; the second, or specific name, is restricted to one species or special kind of animal. And as scientific books were formerly written in Latin because that was the common language of scientific men, so Latin is still used for the names. It must be understood that a scientific name does not necessarily mean anything; it is simply a handle by which to lay hold of some particular kind of animal, and had such a method been agreed upon, the species might have been lettered and numbered, much as astronomers have done with the stars.

Representatives of the larger divisions, or classes, of back-boned animals are familiar to most of us, but there is an unfortunate tendency to confine the name animal to mammals, instead of allowing it to include, as it properly does, all forms of animate things, or animals, from the microscopic, single-celled being which finds a bucket of water an ample world, up to man.

The warm-blooded, air-breathing mammals, whose young are born alive[3] and helpless, and are nursed by their mothers until old enough to care for themselves, we all know. Some of them, it is true, are more or less disguised by adaptation to some particular mode of life, but if we strip off these disguises their identity is revealed, for we find them all built on the same plan. There is little outside resemblance between the hand of a monkey, the hoof of a horse, the wing of a bat, and the paddle of a whale, and yet the same parts are present in all. The whale wears mittens, and the more aristocratic monkey gloves, but they have the same bones as ourselves. Note, too, that habits and place of residence are not characters; the whale is just as much at home in the water as the fish, and the bat is more expert on the wing than many birds, but the one is not a fish nor is the other a bird; both are equally mammals. Dress, however, does count for something in the rest of the animal kingdom, if not so much as it does with us, but it may not be used as the basis of classification, only as a help to distinguish species from one another. Most mammals are clothed in hair or fur, but many go naked, especially in warm climates, and so do the whales, in order that they may slip through the water readily.[4] The armadillos are protected by an armor of bone, and their cousins, the pangolins of Asia and Africa, by an even more effective armor of sharp-edged, overlapping horny scales.

Birds are familiar to all, and even the kiwis and penguins, which depart most in appearance from their fellows, are easily recognized as birds, so the class may be passed by with little further notice other than to say that its members are almost as uniform in the matter of internal structure as they are in external appearance, and that both are modified according as they fly, run, or swim. The divisions of this class are not so sharply defined as are those of other groups of vertebrates, but the crow and ostrich may be taken as representatives of the two principal subdivisions. This is not merely because the one can fly and the other can not—for there are birds related to the ostrich which possess the power of flight, while certain relatives of the crow are flightless—but on account of peculiarities found in the skull and hip bones of these birds.

Reptiles, too, are fairly well defined in the minds of most of us, although some uncertainty may now and then exist as to whether or not the Amphibia should be included with them. Crocodiles, lizards, snakes, and turtles are familiar and typical examples of this class, but, as we shall see later on, the largest and most striking members of the group, comprising hundreds of species and constituting several entire orders, died out long ago, and are known only from fossils. The Amphibia include not only such creeping and crawling things as newts, salamanders, and mud-puppies, but frogs and toads, a small number of curious little snake-like creatures, and a large number of extinct species, including very many of almost gigantic size. These last form an order by themselves, which was of no little importance in the ancient world. So far as size, number, and distribution are concerned, the reptiles and amphibians of to-day are a degenerate lot, and it is difficult to imagine that they were successively the dominant forms of life, as common and as widely spread over the world as mammals are to-day.

Under the comprehensive term Fishes are really included three divisions or classes of equal rank in classification, though very unequal in the number of species. One of these is represented by the lowly little lancelet, which has no skull even, and can barely be considered a vertebrate; another contains the lampreys and their relatives, more or less distant; while the third comprises the sharks, chimeras, sturgeons, and the hosts of true or bony fishes which form the vast majority of the class. The lampreys, which deserve more than passing notice, because they will often be referred to, have no jaws or limbs, and a soft backbone without even a hint of divisions into joints or vertebræ. Still, low as they are in the scale of vertebrate life, they date back almost to its commencement; though while they may be respected for their ancient lineage, they may also serve as a warning that fortunately the importance of a family does not depend upon the length of its pedigree.