THE DESCENT OR OBIGIN OF MAN 87 



tail originally had been bent round, by the will of the ani- 

 mal, into the interspace between the callosities, to escape 

 being pressed between them and the ground, and that in 

 time the curvature became permanent, fitting in of itself 

 when the organ happens to be sat upon." Under these 

 circumstances it is not surprising that the surface of the 

 tail should have been roughened and rendered callous; 

 and Dr. Murie," who carefully observed this species in 

 the Zoological Gardens, as well as three other closely allied 

 forms with slightly longer tails, says that when the animal 

 sits down, the tail "is necessarily thrust to one side of the 

 buttocks; and whether long or short its root is consequently 

 liable to be rubbed or chafed." As we now have evidence 

 that mutilations occasionally produce an inherited effect,** 

 it is not very improbable that in short-tailed monkeys the 

 projecting part of the tail, being functionally useless, should 

 after many generations have become rudimentary and dis- 

 torted, from being continually rubbed and chafed. "We see 

 the projecting part in this condition in the Macacus brunneus, 

 and absolutely aborted in the M. ecaudatus and in several of 

 the higher apes. Finally, then, as far as we can judge, the 

 tail has disappeared in man and the anthropomorphous apes, 

 owing to the terminal portion having been injured by friction 

 during a long lapse of time; the basal and imbedded portion 

 having been reduced and modified, so as to become suitable 

 to the erect or semi-erect position. 



I have now endeavored to show that some of the most 

 distinctive characters of man have in all probability been 

 acquired, either directly, or, more commonly, indirectly, 

 through natural selection. We should bear in mind that 



»8 "Proo. Zoolog. Soc," 1872, p. 786. 



"* I allude to Dr. Brown-S^quard's observations on the transmitted effect 

 of an opera, ion causing epilepsy in guinea-pigs, and likewise more recently on 

 the analogoiiS efEecls of cutting the sympathetic nerve in the neck. I shall here- 

 after have o'jcasion to refer to Mr. Salvia's iijtereating case of the apparently 

 inherited ejiects of mot-mots biting ofl the barbs of their own tail-feathers. 

 See also, on the general subject, "Variation of Animals and Plants undw 

 Domeslicati'.n," voL ii. pp. 22-24. 



