The Atlantic Monthly, Volume 09, No. 51, January, 1862. Various
members of the larger groups, Linnæus gave to them names that should be common to all, and which are called generic names,—as we speak of Ducks, when we would designate in one word the Mallard, the Widgeon, the Canvas-Back, etc.; but to these generic names he added qualifying epithets, called specific names, to indicate the different kinds in each group. For example, the Lion, the Tiger, the Panther, the Domestic Cat constitute such a natural group, which Linnæus called Felis, Cat, indicating the whole genus; but the species he designates as Felis catus, the Domestic Cat,—Felis leo, the Lion,—Felis tigris, the Tiger,—Felis panthera, the Panther. So he called all the Dogs Canis; but for the different kinds we have Canis familiaris, the Domestic Dog,—Canis lupus, the Wolf,—Canis vulpes, the Fox, etc.
In some families of the vegetable kingdom we can appreciate better the application of this nomenclature, because we have something corresponding to it in the vernacular. We have, for instance, one name for all the Oaks, but we call the different kinds Swamp Oak, Red Oak, White Oak, Chestnut Oak, etc. So Linnæus, in his botanical nomenclature, called all the Oaks by the generic name Quercus, (characterizing them by their fruit, the acorn, common to all,) and qualified them as Quercus bicolor, Quercus rubra, Quercus alba, Quercus castanea, etc., etc. His nomenclature, being so easy of application, became at once exceedingly popular and made him the great scientific legislator of his century. He insisted on Latin names, because, if every naturalist should use his own language, it must lead to great confusion, and this Latin nomenclature of double significance was adopted by all. Another advantage of this binominal Latin nomenclature consists in preventing the confusion frequently arising from the use of the same name to designate different animals in different parts of the world,—as, for instance, the name of Robin, used in America to designate a bird of the Thrush family, entirely different from the Robin of the Old World,—or of different names for the same animal, as Perch or Chogset or Burgall for our Cunner. Nothing is more to be deprecated than an over-appreciation of technicalities, valuing the name more highly than the thing; but some knowledge of this nomenclature is necessary to every student of Nature.
The improvements in science thus far were chiefly verbal. Cuvier now came forward and added a principle. He showed that all animals are built upon a certain number of definite plans. This momentous step, the significance of which is not yet appreciated to its full extent; for, had its importance been understood, the efforts of naturalists would have been directed toward a further illustration of the distinctive characteristics of all the plans,—instead of which, the division of the animal kingdom into larger and smaller groups chiefly attracted their attention, and has been carried too far by some of them. Linnæus began with six classes, Cuvier brought them up to nineteen, and at last the animal kingdom was subdivided by subsequent investigators into twenty-eight classes. This multiplication of divisions, however, soon suggested an important question: How far are these divisions natural or inherent in the objects themselves, and not dependent on individual views?
While Linnæus pointed out classes, orders, genera, and species, other naturalists had detected other divisions among animals, called families. Lamarck, who had been a distinguished botanist before he began his study of the animal kingdom, brought to his zoölogical researches his previous methods of investigation. Families in the vegetable kingdom had long been distinguished by French botanists; and one cannot examine the groups they call by this name, without perceiving, that, though they bring them together and describe them according to other characters, they have been unconsciously led to unite them from the general similarity of their port and bearing. Take, for instance, the families of Pines, Oaks, Beeches, Maples, etc., and you feel at once, that, besides the common characters given in the technical descriptions of these trees, there is also a general resemblance among them that would naturally lead us to associate them together, even if we knew nothing of the other features of their structure. By an instinctive recognition of this family likeness between plants, botanists have been led to seek for structural characters on which to unite them, and the groups so founded generally correspond with the combinations suggested by their appearance.
By a like process Lamarck combined animals into families. His method was adopted by French naturalists generally, and found favor especially with Cuvier, who was particularly successful in limiting families among animals, and in naming them happily, generally selecting names expressive of the features on which the groups were founded, or borrowing them from familiar animals. Much, indeed, depends upon the pleasant sound and the significance of a name; for an idea reaches the mind more easily when well expressed, and Cuvier’s names were both simple and significant. His descriptions are also remarkable for their graphic precision,—giving all that is essential, omitting all that is merely accessory. He has given us the key-note to his progress in his own expressive language:—
“Je dus donc, et cette obligation me prit un temps considérable, je dus faire marcher de front l’anatomie et la zoologie, les dissections et le classement; chercher dans mes premières remarques sur l’organisation des distributions meilleures; m’en servir pour arriver à des remarques nouvelles; employer encore ces remarques à perfectionner les distributions; faire sortir enfin de cette fécondation mutuelle des deux sciences, l’une par l’autre, un système zoologique propre à servir d’introducteur et de guide dans le champ de l’anatomie, et un corps de doctrine anatomique propre à servir de développement et d’explication au système zoologique.”
It is deeply to be lamented that so many naturalists have entirely overlooked this significant advice of Cuvier’s, to combine zoölogical and anatomical studies in order to arrive at a clearer perception of the true affinities among animals. To sum it up in one word, he tells us that the secret of his method is “comparison,”—ever comparing and comparing throughout the enormous range of his knowledge of the organization of animals, and founding upon the differences as well as the similarities those broad generalizations under which he has included all animal structures. And this method, so prolific in his hands, has also a lesson for us all. In this country there is a growing interest in the study of Nature; but while there exist hundreds of elementary works illustrating the native animals of Europe, there are few such books here to satisfy the demand for information respecting the animals of our land and water. We are thus forced to turn more and more to our own investigations and less to authority; and the true method of obtaining independent knowledge is this very method of Cuvier’s,—comparison.
Let us make the most common application of it to natural objects. Suppose we see together a Dog, a Cat, a Bear, a Horse, a Cow, and a Deer. The first feature that strikes us as common to any two of them is the horn in the Cow and Deer. But how shall we associate either of the others with these? We examine the teeth, and find those of the Dog, the Cat, and the Bear sharp and cutting, while those of the Cow, the Deer, and the Horse have flat surfaces, adapted to grinding and chewing, rather than cutting and tearing. We compare these features of their structure with the habits of these animals, and find that the first are carnivorous, that they seize and tear their prey, while the others are herbivorous or grazing animals, living only on vegetable substances, which they chew and grind. We compare farther the Horse and Cow, and find that the Horse has front teeth both in the upper and lower jaw, while the Cow has them only in the lower; and going still farther and comparing the internal with the external features, we find this arrangement of the teeth in direct relation to the different structure of the stomach in the two animals,—the Cow having a stomach with four pouches, adapted to a mode of digestion by which the food is prepared for the second mastication, while the Horse has a simple stomach. Comparing the Cow and the Deer, we find that the digestive apparatus is the same in both; but though they both have horns, in the Cow the horn is hollow, and remains through life firmly attached to the bone, while in the Deer it is solid and is shed every year. With these facts before us, we cannot hesitate to place the Dog, the Cat, and the Bear in one division, as carnivorous animals, and the other three in another division as herbivorous animals,—and looking a little farther, we perceive, that, in common with the Cow and the Deer, the Goat and the Sheep have cloven feet, and that they are all ruminants, while the Horse has a single hoof, does not ruminate, and must therefore be separated from them, even though, like them, he is herbivorous.
This is but the simplest illustration, taken from the most familiar objects, of this comparative method; but the same process is equally applicable to the most intricate problems in