lived and written since the publication of the researches of modern Egyptologists, and Owen's latest and most emphatic utterances have been made subsequently to the appearance of even the "Types of Mankind," we are not at liberty to assign such an explanation of their zoological errors.

We have extended our remarks to an inconvenient, and, we fear, a tedious length, in illustration of the doctrine that varieties, when kept separate by breeding inter se, are often as permanent as species, because the denial of this fact is a cardinal point with those who deny the unity of the human species. Admit this doctrine, which, it does appear to us, no reasonable mind can now reject, and the "monumental history," discovered in Egypt, only proves that some of the now existing varieties of men and dogs had their origin prior to the date of the inscriptions. Assign to these the earliest date you please, there must, of course, have been several centuries between that period and the commencement of the world's history. The inscriptions prove that such and such varieties existed so many thousand years ago. Granted. We ourselves contend that certain varieties are permanent. But when you conclude that, because the types have not changed since those inscriptions. were made, therefore they were created as distinct species, we can not withhold an expression of surprise that you overlook the obvious flaw in your argument, and we protest against the manifest petitio principii. Sir C. Lyell has shown that species, susceptible of modification, may be greatly altered in a few generations. Indeed, in all the instances of such variations, in which the process has been made known, the maximum amount of change was reached in a comparatively short time, and thenceforward the newly acquired characters were regularly transmitted by descent. We have already cited a number of instances from among the lower animals. We shall, in the sequel, have occasion to refer to the occurrence of similar phenomena in the human family within historic, and even modern times.

Assuming, then, as now sufficiently well proved, the doctrine that varieties may spring up within the limits of a single pecies, and be permanently perpetuated, the question pre

* Principles of Geology, p. 570.

sents itself, how are we to recognize such groups? or in other words, how can we ascertain whether two groups of individuals, possessing numerous points of resemblance, but yet marked by some distinctive features, are distinct species, or are only permanent varieties of one species? Of course, the most satisfactory and conclusive test would be authentic historical evidence, going back to the origin of a given race. This test is especially important, as not only settling the question in any particular case in regard to which it may have been collected, but as verifying data, which, on the grounds of analogy, we may apply to other cases where direct historical evidence is wanting. It furnishes us with examples of known variation, and indicates at the same time the extent and direction of possible changes that are yet compatible with specific unity. It has brought to light the interesting fact, that there is a great diversity in respect to capacity for variation among animals, even those that are most nearly allied to each other in other particulars. Hence, some not possessing this capacity are restricted to particular conditions of climate, food, etc., while others are more widely dispersed, simply because they have the power of adapting their physical and psychical constitutions to a wider range of conditions.* It also proves that "some mere varieties are possibly more distinct than certain individuals of distinct species." A most admirable exposition of the final causes of this providential arrangement is found in the chapter of Lyell's Principles of Geology, to which we are indebted for many of the facts and arguments already given. "If it be a law, for instance, that scanty sustenance should check those individuals in their growth, which are enabled to accommodate themselves to privations of this kind, and that a parent, prevented in this manner from attaining the size proper to its species, should produce a dwarfish offspring, a stunted race will arise, as is remarkably exemplified in some varieties of the horse and dog. The difference of stature in some races of dogs, when compared to others, is as one to five in linear dimensions, making a difference of a hundred-fold in volume. Now, there is

*W. B. Carpenter. Varieties of Mankind.

+ Lyell. Principles of Geology.

good reason to believe that species in general are by no means susceptible of existing under a diversity of circumstances, which may give rise to such a disparity of size, and, consequently, there will be a multitude of distinct species, of which no two adult individuals can ever depart so widely from a certain standard of dimensions as the mere varieties of certain other species-the dog, for instance. Now we have only to suppose that what is true of size, may also hold with regard to color, and many other attributes; and it will at once follow that the degree of possible discordance between varieties of the same species may, in certain cases, exceed the utmost disparity which can arise between two individuals of many distinct species. The same remarks may hold true in regard to instincts; for, if it be foreseen that one species will have to encounter a great variety of foes, it may be necessary to arm it with great cunning and circumspection, or with courage, or other qualities capable of developing themselves on certain ccasions; such, for example, as those migratory instincts which are so remarkably exhibited at particular periods, after they have remained dormant for many generations. The history and habits of one variety of such species, may often differ more considerably from some other than those of many listinct species, which have no such latitude of accommodation to circumstances."

The horse, the dog, horned cattle, swine, and in a word, all the domesticated animals which follow man in his migrations, and like him manifest a power of accommodation to widely varied conditions of climate, exhibit also, as has already been intimated, an extraordinary capacity for variation, so that mere varieties arising within the limits of any one of these species, ay the hog, in regard to which we have already cited unquestionable facts that will serve to illustrate the point now under consideration, will exhibit differences far greater in apparent gnificance than in other cases would suffice to indicate specific distinctions.

The question now recurs whether, when historical proof can not be had, there is any other mode of ascertaining whether two or more groups of somewhat dissimilar animals are dif

ferent but allied species, like tigers and leopards, or are only permanent varieties of one species, like the different breeds. of hogs which are known to have sprung from a common stock.

Adverting to the fact that it is the constancy of a differential character, however intrinsically unimportant it may appear, which serves to indicate the distinction of species, we are prepared to understand that next to historical evidence, tracing a given stock through a long interval of time and under great variations of external conditions, so as to note the successive changes it may have undergone, the most important source of information is found in obtaining an assemblage of as many forms as possible of each type, with the view of comparing them with each other for the sake of determining whether the supposed specific characters are constant and well marked throughout, or whether diverse forms tend to run together by intermediate gradations. We are indebted to Dr. Carpenter for an apt illustration of the principle in question. "Two Terebratulæ (a genus of Brachiopod Bivalves) are brought to us from different parts of the great Southern Ocean, the one of which has the edges of the valves of the shells thrown into deep plications, whilst in the other they are quite smooth. Now in most other Bivalve Molluscans such a difference would be justly admitted to afford a valid specific character, and the conchologist, who had only these two shells before him, would be fully justified, by the usual rules of the science, in ranking each as a distinct specific type. But as his collection extends, intermediate forms come into his possession; and at last he finds that he can make a continuous series, passing, by the most gradual transition, from the smoothest to the most deeply plirated form. Thus, then, the supposed validity of this distinction is altogether destroyed; and it becomes evident that the most plicated and the smoothest of these Terebratulæ must be regarded as belonging to one and the same species, notwithstanding the marked diversity of their extreme forms."* It is on similar grounds that the most eminent naturalists admit the specific unity of all the diversified varieties of the dog. As was well remarked by F. Cuvier, there is no alter*W. B Carpenter. "Varieties of Mankind," in the Cyclopædia of Anatomy and Physiology.

native between adopting this conclusion and falling into the absurdity of admitting at least fifty species of dogs, all distinguished by permanent differences, and yet capable of unlimited cross-breeding. Prof. R. Owen insists upon the same doctrine. Adverting to the extraordinary differences in cranial conformation between the large greyhound on the one hand and the smaller spaniel on the other, he adds: "But yet under the extremest mask of variety so superinduced, the naturalist detects in the dental formula, and in the construction of the cranium, the unmistakable generic and specific characters of the canis familiaris."* We have just seen, it is true, that the authors of the "Types of Mankind" attempt to discredit the conclusions of naturalists with reference to the specific unity of the dog, by having recourse to Egyptian monumental inscriptions, which, however, only serve to show that some of the now existing varieties had already arisen prior to the date of those inscriptions. They do not touch the question of their origin, and we are, therefore, constrained to treat the question on the principles, the validity of which is fully recognized by all philosophical naturalists. Let it be observed too, that whatever be the original cause of these variations, even when some of them appear to depend on climate, as soon as they become permanent they are transmitted irrespectively of the continued operation of the causes that had given rise to them; so that breeds originating in different localities, under the influence of different conditions connected with climate, after being once established will be perpetuated without change in one and the same climate. A noteworthy and interesting exception to this remark is found in the case of the lapse of domesticated breeds into the wild state, when the va rieties dependent on domestication are likely to merge into one common type, which approximates more or less closely to the original stock whence the domestic breeds had sprung. According to Dr. Carpenter,† this change has taken place in various parts of the world in the case of dogs, (the very case, namely, in which Dr. Nott contends that types are so permanent,) which were introduced from Europe and which have

Zoological Transactions, vol. iii. + W. B. Carpenter's Zoology, vol. i. p. 85.