fatal effects; and is plagued by external parasites, all of which belong to the same genera or families as those infesting other mammals, and in the case of scabies to the same species. Man is subject, like other mammals, birds, and even insects, to that mysterious law, which causes certain normal processes, such as gestation, as well as the maturation and duration of various diseases, to follow lunar periods. His wounds are repaired by the same process of healing; and the stumps left after the amputation of his limbs, especially during an early embryonic period, occasionally possess some power of regeneration, as in the lowest animals.10

The whole process of that most important function, the reproduction of the species, is strikingly the same in all mammals, from the first act of courtship by the male," to the birth and nurturing of the young. Monkeys are born in almost as helpless a condition as our own infants; and in certain genera the young differ fully as much in appearance from the adults, as do our children from their full-grown parents.12 It has been urged by some writers, as an important distinction, that with man the young arrive at maturity at a much later age than with any other animal: but if we look to the races of mankind which inhabit tropical countries the difference is not great, for the orang is believed not to be adult till the age of from ten to fifteen years.18 Man differs from woman in size, bodily strength, hairiness, &c., as well as in mind, in the same manner as do the

Dr. W. Lauder Lindsay, 'Edinburgh Vet. Review,' July 1858, p. 13.

9 With respect to insects see Dr. Laycock, "On a General Law of Vital Periodicity," British Association,' 1842. Dr Macculloch, Silliman's North American Journal of Science,' vol. xvii. p. 305, has seen a dog suffering from tertian ague. Hereafter I shall return to this subject.

10 I have given the evidence on this head in my Variation of Animals and Plants under Domestication,' vol. ii. p. 15, and more could be added.

per eligebat juniores, et dignos"cebat in turba, et advocabat voce gestûque."

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12 This remark is made with respect to Cynocephalus and the anthropomorphous apes by Geoffroy Saint-Hilaire and F. Cuvier, 'Hist. Nat. des Mammifères,' tom. i. 1824.

13 Huxley, Man's Place in Na ture,' 1863, p. 34.

two sexes of many mammals. So that the correspondence in general structure, in the minute structure of the tissues, in chemical composition and in constitution, between man and the higher animals, especially the anthropomorphous apes, is extremely close.

Embryonic Development.-Man is developed from an ovule, about the 125th of an inch in diameter, which differs in no respect from the ovules of other animals. The embryo itself at a very early period can hardly be distinguished from that of other members of the vertebrate kingdom. At this period the arteries run in arch-like branches, as if to carry the blood to branchia which are not present in the higher vertebrata, though the slits on the sides of the neck still remain (f, g, fig. 1), marking their former position. At a somewhat later period, when the extremities are developed, "the feet of lizards and

14

mammals,” as the illustrious Von Baer remarks, “the wings "and feet of birds, no less than the hands and feet of man, all "arise from the same fundamental form." It is, says Prof. Huxley, "quite in the later stages of development that the young human being presents marked differences from the young ape, while the latter departs as much from the dog in its developments, as the man does. Startling as this last assertion may appear to be, it is demonstrably true."

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As some of my readers may never have seen a drawing of an embryo, I have given one of man and another of a dog, at about the same early stage of development, carefully copied from two works of undoubted accuracy.'5

15

After the foregoing statements made by such high authorities, it would be superfluous on my part to give a number of borrowed details, shewing that the embryo of man closely resembles that of other mammals. It may, however, be added, that the human embryo likewise resembles certain low forms when adult in various points of structure. For instance, the heart at first exists as a simple pulsating vessel; the excreta are voided through a cloacal passage; and the os coccyx projects

Fig. 1. Upper figure human embryo, from Fcker. Lower fgure that of a dog, from Bischoff.

a. Fore-brain, cerebral hemispheres, &c. b. Mid-brain, corpora quadrigemina.

c. Hind-b.ain, cerebellum, medulla ob

longata.

d. Fye.

e. Ear.

f. First visceral arch.

g. Second visceral arch.

H. Vertebral columns and muscles process of development.

i Anterior extremities.

K. Posterior

L. Tail or os coccyx.

like a true tail, extending considerably beyond the rudi"mentary legs."16 In the embryos of all air-breathing vertebrates, certain glands, called the corpora Wolffiana, correspond with, and act like the kidneys of mature fishes." Even at a later embryonic period, some striking resemblances between man and the lower animals may be observed. Bischoff says that the convolutions of the brain in a human foetus at the end of the Seventh month reach about the same stage of development as in a baboon when adult." The great toe, as Prof. Owen remarks,18 "which forms the fulcrum when standing or walking, is perhaps the most characteristic peculiarity in the human structure;" but in an embryo, about an inch in length, Prof. Wyman 20 found "that the great toe was shorter than the others; and, instead of being parallel to them, projected at an angle "from the side of the foot, thus corresponding with the per"manent condition of this part in the quadrumana." I will conclude with a quotation from Huxley," who after asking, does man originate in a different way from a dog, bird, frog or fish? says, "the reply is not doubtful for a moment; without question, the mode of origin, and the early stages of the development of man, are identical with those of the animais immediately below him in the scale: without a doubt in "these respects, he is far nearer to apes than the apes are to "the dog."

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Rudiments. This subject, though not intrinsically more important than the two last, will for several reasons be treated nere more fully.22 Not one of the higher animals can be named which does not bear some part in a rudimentary condition; and man forms no exception to the rule. Rudimentary organs must be distinguished from those that are nascent; though in some cases the distinction is not easy. The former are either absolutely useless, such as the mammæ of male quadrupeds, or the incisor teeth of ruminants which never cut through the gums; or they are of such slight service to their present possessors, that we can hardly suppose that they were developed under the

conditions which now exist. Organs in this latter state are not strictly rudimentary, but they are tending in this direction. Nascent organs, on the other hand, though not fully developed, are of high service to their possessors, and are capable of further development. Rudimentary organs are eminently variable; and this is partly intelligible, as they are useless, or nearly useless, and consequently are no longer subjected to natural selection. They often become wholly suppressed. When this occurs, they are nevertheless liable to occasional reappearance through reversion-a circumstance well worthy of attention.

The chief agents in causing organs to become rudimentary seem to have been disuse at that period of life when the organ is chiefly used (and this is generally during maturity), and also inheritance at a corresponding period of life. The term "disuse" does not relate merely to the lessened action of muscles, but includes a diminished flow of blood to a part or organ, from being subjected to fewer alternations of pressure, or from becoming in any way less habitually active. Rudiments, however, may occur in one sex of those parts which are normally present in the other sex; and such rudiments, as we shall hereafter see, have often originated in a way distinct from those here referred to. In some cases, organs have been reduced by means of natural selection, from having become injurious to the species under changed habits of life. The process of reduction is probably often aided through the two principles of compensation and economy of growth; but the later stages of reduction, after disuse has done all that can fairly be attributed to it, and when the saving to be effected by the economy of growth would be very small,23 are difficult to understand. The final and complete suppression of a part, already useless and much reduced in size, in which case neither compensation nor economy can come into play, is perhaps intelligible by the aid of the hypothesis of pangenesis. But as the whole subject of rudimentary organs has been discussed and illustrated in my former works,24 I need here say no more on this head.

Rudiments of various muscles have been observed in many parts of the human body;25 and not a few muscles, which are

23 Some good criticisms on this subject have been given by Messrs. Murie and Mivart, in Transact. Zoolog. Soc. 1869, vol. vii. p. 92.

24 Variation of Animals and Plants under Domestication,' vol. ii. pp. 317 and 397. See also Origin of Species,' 5th edit. p. 535.

25 For instance M. Richard ('Annales des Sciences Nat.' 3rd series,

Zoolog. 1852, tom. xviii. p. 13) describes and figures rudiments of what he calls the "muscle pédieux de la main," which he says is sometimes "infiniment petit." Another muscle, called "le tibial postérieur," is generally quite absent in the hand, but appears from time to time in a more or less rudimentary condition.