86 



THE DESCENT OF MAN 



tute what Broca calls the accessory sacral vertebrae. These 

 are of functional importance by supporting certain internal 

 parts and in other ways; and their modification is directly 

 connected with the erect 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 modification, therefore, of the 

 basal caudal vertebrsB 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 vari- 

 able vertebrae of the terminal portion of the tail, forming the 

 08 coccyx? 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 externa] 

 portion of the tail, is not so ridiculous as it at first ap- 

 pears. Dr. Anderson" states that the extremely short tail 

 of Macacus hrunneus is formed of eleven vertebra, including 

 the imbedded basal ones. The extremity is tendinous and 

 contains no vertebrae ; this is succeeded by five rudimentary 

 ones, so minute that together they are only one 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 

 vertebrae. This short tail is carried erect; but about a quar- 

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

 this terminal part, which includes the hooklike portion, 

 serves "to fill up the interspace between the upper diver- 

 gent portion of the callosities"; so that the animal sits on 

 it, and thus renders it rough and callous. Dr. Anderson 

 thus sums up his observations: "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 

 ~ *! "Proe. Zoolog. Soc," 1872, p. 210. " 



