Chap. II. Maimer of Development. 59 



or semi-erect attitude of man and the anthropomorphous apes. 

 This conclusion is the more trustworthy, as Broca formerly held 

 a different view, which he has now abandoned. The modifica- 

 tion, therefore, of the basal caudal vertebra in man and the 

 higher apes may have been effected, directly or indirectly, 

 through natural selection. 



But what are we to say about the rudimentary and variable 

 vertebras of the terminal portion of the tail, forming the os coccyx f 

 A notion which has often been, and will no doubt again be 

 ridiculed, namely, that friction has had something to do with 

 the disappearance of the external portion of the tail, is not 

 so ridiculous as it at first appears. Dr. Anderson 92 states 

 that the extremely short tail of Macacus brunneus is formed of 

 eleven vertebras, including the imbedded basal ones. The 

 extremity is tendinous and contains no vertebras; this is suc- 

 ceeded by five rudimentary ones, so minute that together they 

 are only oue line and a half in length, and these are permanently 

 bent to one side in the shape of a hook. The free part of the 

 tail, only a little above an inch in length, includes only four more 

 small vertebras. This short tail is carried erect ; but about a 

 quarter of its total length is doubled on to itself to the left; and 

 this terminal part, which includes the hook-like portion, serves 

 " to fill up the interspace between the upper divergent portion 

 " of the callosities ;" so that the animal sits on it, and thus renders 

 it rough and callous. Dr. Anderson thus sums up his observa- 

 tions : " These facts seem to me to have only one explanation ; 

 " this tail, from its short size, is in the monkey's way when it 

 " sits down, and frequently becomes placed under the animal 

 " while it is in this attitude ; and from the circumstance that it 

 " does not extend beyond the extremity of the ischial tuberosities 

 " it seems as if the tail originally had been bent round, by the 

 w will of the animal, 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 circum- 

 stances it is not surprising that the surface of the tail should 

 have been roughened and rendered callous; and Dr. Murie, 93 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 

 u is consequently liable to be rubbed or chafed." As we now 



92 < Proc. Zoolog. Soc.,' 1872, p. 93 « Proc Zoolog. See. 1 872, p 



210. 786. 



