MANNER OF DEVELOPMENT. 59 



animal could not have been gradually converted from a 

 quadruped into a biped, as all the individuals in an inter- 

 mediate condition would have been miserably ill-fitted for 

 progression. But we know (and this is well worthy of re- 

 flection) that the anthropomorphous apes are now actually 

 in an intermediate condition ; and no one doubts that they 

 are on the whole well adapted for their conditions of life. 

 Thus the gorilla runs with a sidelong shambling gait, but 

 more commonly progresses by resting on its bent hands. 

 The long-armed apes occasionally use their arms like 

 crutches, swinging their bodies forward between them, and 

 some kinds of Hylobates, without having been taught, can 

 walk or run upright with tolerable quickness ; yet they 

 move awkwardly and much less securely than man. AVe 

 see, in short, in existing monkeys a manner of progression 

 intermediate between that of a quadruped and a biped; 

 but, as an unprejudiced judge* insists, the anthropo- 

 morphous apes approach in structure more nearly to the 

 bipedal than to the quadrupedal type. 



As the progenitors of man became more and more erect, 

 with their hands and arms more and more modified for 

 prehension and other purposes, with their feet and legs at 

 the same time transformed for firm support and progres- 

 sion, endless other changes of structure would have be- 

 come necessary. The pelvis would have to be broadened, 

 the spine peculiarly curved, and the head fixed m an 

 altered position, all of which changes have been attained 

 by man. Prof. Schaaffhausenf maintains that *^the pow- 

 erful mastoid processes of the human skull are the result 

 of his erect position;" and these processes are absent in 

 the orang, chimpanzee, etc., and are smaller in the go- 

 rrilla than in man. Various other structures, which appear 

 connected with man's erect position, might here have been 

 added. It is very difficult to decide how far these corre- 

 lated modifications are the result of natural selection, and 

 how far of the inherited effects of the increased use of cer- 

 tain parts or of the action of one part on another. 



* Prof. Broca, La Constitution des Vertebres caudales ; " La Revue 

 d'Anthropologie," 1872. p. 26 (separate copy). 



f "On the Primitive Form of the Skull," translated in "Anthrop- 

 ological Review," Oct. 1868, p. 428. Owen ("Anatomy of Verte- 

 brates," vol. ii, 1866, p. 531) on the mastoid processes in the higher 

 apes. 



