148 
THE DESCENT OF MAN. 
Part I. 
cephalic; for instance, of two skulls of nearly equal 
breadth, the one from a wild rabbit and the other from 
a large domestic kind, the former was only 3*15 and the 
latter 4*3 inches in length. 75 One of the most marked 
distinctions in different races of man is that the skull 
in some is elongated, and in others rounded ; and here 
the explanation suggested by the case of the rabbits 
may partially hold good ; for Welcker finds that short 
“ men incline more to brachycephaly, and tall men to 
dolichocephaly ; ” 76 and tall men may be compared with 
the larger and longer-bodied rabbits, all of which have 
elongated skulls, or are dolichocephalic. 
From these several facts we can to a certain ex- 
tent understand the means through which the great 
size and more or less rounded form of the skull has 
been acquired by man ; and these are characters emi- 
nently distinctive of him in comparison with the lower 
animals. 
Another most conspicuous difference between man and 
the lower animals is the nakedness of his skin. Whales 
and dolphins (Cetacea), dugongs (Sirenia) and the hip- 
popotamus are naked ; and this may be advantageous 
to them for gliding through the water; nor would it 
be injurious to them from the loss of warmth, as the 
species which inhabit the colder regions are protected 
by a thick layer of blubber, serving the same purpose 
as the fur of seals and otters. Elephants and rhino- 
ceroses are almost hairless ; and as certain extinct 
species which formerly lived under an arctic climate 
were covered with long wool or hair, it would almost 
appear as if the existing species of both genera had lost 
75 ‘ Variation of Animals/ &c., vol. i. p. 117 on the elongation of the 
skull; p. 119, on the effect of the lopping of one ear. 
76 Quoted by Schaaifhausen, in ‘ Anthropdog. Review/ Oct. 1868, 
p. 41*9. 
