148 THE DESCENT OP MAN. 



between the arrangement of the hair on the limbs, and the course 

 of the medullary arteries." 



It must not be supposed that the resemblances between man 

 and certain apes in the above and many other points — such as in 

 having a naked forehead, long tresses on the head, &c. — are all 

 necessarily the result of unbroken inheritance from a common 

 progenitor, or of subsequent reversion. Many of these resem- 

 blances are more probably due to analogous variation, which 

 follows, as I have elsewhere attempted to show," from co-de- 

 scended organisms having a similar constitution, and having been 

 acted on by like causes inducing similar modifications. With re- 

 spect to the similar direction of the hair on the fore-arms of man 

 and certain monkeys, as this character is common to almost all 

 the anthropomorphous apes, it may probably be attributed to in- 

 heritance; but this is not certain, as some very distinct American 

 monkeys are thus characterized. 



Although, as we have now seen, man has no just right to form 

 a separate Order for his own reception, he may perhaps claim a 

 distinct Sub-order or Family. Prof. Huxley, in his last work," 

 divides the Primates into three Sub-orders; namely, the An- 

 thropidse with man alone, the Simiadse including monkeys of all 

 kinds, and the Lemuridae with the diversified genera of lemurs. 

 As far as differences in certain important points of structure are 

 concerned, man may no doubt rightly claim the rank of a Sub- 

 order; and this rank is too low if we look chiefly to his mental 

 faculties. Nevertheless, from a genealogical point of view it 

 appears that this rank is too high, and that man ought to form 

 merely a Family, or possibly even only a Sub-family. If we 

 imagine three lines of descent proceeding from a common stock, 

 it is quite conceivable that two of them might after the lapse of 

 ages be so slightly changed as still to remain as species of the 

 same genus, whilst the third line might become so greatly modi- 

 fied as to deserve to rank as a distinct Sub-family, Family, or 

 even Order. But in this case it is almost certain that the third 

 line would still retain through inheritance numerous small points 

 of resemblance with the other two. Here, then, would occur 

 the difficulty, at present insoluble, how much weight we ought 

 to assign in our classifications to strongly-marked differences in 

 some few points, — that is, to the amount of modification under- 



» On the hair in Hylobates, see 'Nat. Hist, of Mammals," by C. L. 

 Martin, 1841, p. 415. Also, Isid. Geoftroy on the American monkeys and 

 other kinds, 'Hist. Nat. Gen.' vol. ii. 1859, p. 216, 243. Bschricht ibid. 

 s. 46, 55, 61. Owen, 'Anat. of Vertebrates," vol. iii. p. 619. Wallace, 'Con- 

 tributions to the Theory of Natural Selection," 1870, p. 344. 



'» 'Origin of Species," 5th edit. 1869, p. 194. 'The Variation of Animals 

 and Plants under Domestication," vol. ii. 1868, p. 348. 



^ 'An Introduction to the Classification of Animals,' 1869, p. 99. 



