MANNER OF BE VELOPMENT. 67 



beyond the extremity of the ischial tuberosities, it seems as 

 if the tail originally had been bent round by the will of the 

 animal, into the interspace between the callosities, to es- 

 cape 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 

 eits down the tail '^ is necessarily thrust to one side of the 

 buttocks; and Avhether 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, f 

 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 distorted, from being continually rubbed and chafed. 

 We see the projecting part in this condition in the Maca- 

 cus hrunneus, 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 embedded 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 

 modifications in structure or constitution which do not 

 serve to adapt an organism to its habits of life, to the food 



*"Proc. Zoolog. Soc," 1872, p. 786. 



f I allude to Dr. Brown-Sequard's observations on the transmitted 

 effect of an operation causing epilepsy in guinea-pigs, and likewise 

 more recently on the analogous effects of cutting the sympathetic 

 nerve in the neck. I shall hereafter have occasion to refer to Mr. 

 Salvin's interesting case of the apparently inherited effects of mot- 

 mots biting off the barbs of their own tail feathers. See also on the 

 general subject "Variation of Animals and Plants under Domesti- 

 cation," vol. ii, pp. 22-34 



