As to the origin of the technical name; ἀστακός, astakos, was the name by which the Greeks knew the lobster; and it has been handed down to us in the works of Aristotle, who does not seem to have taken any special notice of the crayfish. At the revival of learning, the early naturalists noted the close general similarity between the lobster and the crayfish; but, as the latter lives in fresh water, while the former is a marine animal, they called the crayfish, in their Latin, Astacus fluviatilis, or the “river-lobster,” by way of distinction; and this nomenclature was retained until, about forty-five years ago, an eminent French Naturalist, M. Milne-Edwards, pointed out that there are far more extensive differences between lobsters and crayfish than had been supposed; and that it would be advisable to mark the distinctness of the things by a corresponding difference in their names. Leaving Astacus for the crayfishes, he proposed to change the technical name of the lobster into Homarus, by latinising the old French name “Omar,” or “Homar” (now Homard), for that animal.
At the present time, therefore, while the recognised technical name of the crayfish is Astacus fluviatilis, that of the lobster is Homarus vulgaris. And as this nomenclature is generally received, it is desirable that it should not be altered; though it is attended by the inconvenience, that Astacus, as we now employ the name, does not {14} denote that which the Greeks, ancient and modern, signify, by its original, astakos; and does signify something quite different.
Finally, as to why it is needful to have two names for the same thing, one vernacular, and one technical. Many people imagine that scientific terminology is a needless burden imposed upon the novice, and ask us why we cannot be content with plain English. In reply, I would suggest to such an objector to open a conversation about his own business with a carpenter, or an engineer, or, still better, with a sailor, and try how far plain English will go. The interview will not have lasted long before he will find himself lost in a maze of unintelligible technicalities. Every calling has its technical terminology; and every artisan uses terms of art, which sound like gibberish to those who know nothing of the art, but are exceedingly convenient to those who practise it.
In fact, every art is full of conceptions which are special to itself; and, as the use of language is to convey our conceptions to one another, language must supply signs for those conceptions. There are two ways of doing this: either existing signs may be combined in loose and cumbrous periphrases; or new signs, having a well-understood and definite signification, may be invented. The practice of sensible people shows the advantage of the latter course; and here, as elsewhere, science has simply followed and improved upon common sense. {15}
Moreover, while English, French, German, and Italian artisans are under no particular necessity to discuss the processes and results of their business with one another, science is cosmopolitan, and the difficulties of the study of Zoology would be prodigiously increased, if Zoologists of different nationalities used different technical terms for the same thing. They need a universal language; and it has been found convenient that the language shall be the Latin in form, and Latin or Greek in origin. What in English is Crayfish, is Écrevisse in French; Flusskrebs, in German; Cammaro, or Gambaro, or Gammarello, in Italian: but the Zoologist of each nationality knows that, in the scientific works of all the rest, he shall find what he wants to read under the head of Astacus fluviatilis.
But granting the expediency of a technical name for the Crayfish, why should that name be double? The reply is still, practical convenience. If there are ten children of one family, we do not call them all Smith, because such a procedure would not help us to distinguish one from the other; nor do we call them simply John, James, Peter, William, and so on, for that would not help us to identify them as of one family. So we give them all two names, one indicating their close relation, and the other their separate individuality—as John Smith, James Smith, Peter Smith, William Smith, &c. The same thing is done in Zoology; only, in accordance with the genius of the Latin language, {16} we put the Christian name, so to speak, after the surname.
There are a number of kinds of Crayfish, so similar to one another that they bear the common surname of Astacus. One kind, by way of distinction, is called fluviatile, another slender-handed, another Dauric, from the region in which it lives; and these double names are rendered by—Astacus fluviatilis, Astacus leptodactylus, and Astacus dauricus; and thus we have a nomenclature which is exceedingly simple in principle, and free from confusion in practice. And I may add that, the less attention is paid to the original meaning of the substantive and adjective terms of this binomial nomenclature, and the sooner they are used as proper names, the better. Very good reasons for using a term may exist when it is first invented, which lose their validity with the progress of knowledge. Thus Astacus fluviatilis was a significant name so long as we knew of only one kind of crayfish; but now that we are acquainted with a number of kinds, all of which inhabit rivers, it is meaningless. Nevertheless, as changing it would involve endless confusion, and the object of nomenclature is simply to have a definite name for a definite thing, nobody dreams of proposing to alter it.
Having learned this much about the origin of the names of the crayfish, we may next proceed to consider those points which an observant Naturalist, who did not {17} care to go far beyond the surface of things, would find to notice in the animal itself.
Probably the most conspicuous peculiarity of the crayfish, to any one who is familiar only with the higher animals, is the fact that the hard parts of the body are outside and the soft parts inside; whereas in ourselves, and in the ordinary domestic animals, the hard parts, or bones, which constitute the skeleton, are inside, and the soft parts clothe them. Hence, while our hard framework is said to be an endoskeleton, or internal skeleton; that of the crayfish is termed an exoskeleton, or external skeleton. It is from the circumstance that the body of the crayfishes is enveloped in this hard crust, that the name of Crustacea is applied to them, along with the crabs, shrimps, and other such animals. Insects, spiders, and centipedes have also a hard exoskeleton, but it is usually not so hard and thick as in the Crustacea.