CHAPTEE I 



MAMMALS 



Primates. The male gorilla differs considerably from 

 the female. Darwin says it is believed to be polygamous, 

 and cites this as evidence in favour of the occurrence of 

 sexual selection. There is a great difference in the skull 

 between the two sexes, the peculiarity in the male being 

 chiefly related to the great development of canine teeth. 

 Male gorillas fight much, and the canine teeth are their chief 

 weapons. Granting that the use of the teeth gradually 

 increases their size, and that the general exertion of muscles 

 has an inherited effect, the unisexual characters of the male 

 gorilla in canines, size, and strength are explained. The 

 sagittal crest is strongly marked in the male, absent in the 

 female, and this is connected with the great extension of 

 the attachment of the temporal muscle in the male, one of 

 the chief muscles which are employed in biting. Another 

 peculiarity of the male gorilla is his voice, and he is furnished 

 with a laryngeal sac, as likewise is the male orang. Here 

 there is no difficulty in tracing the direct effects of exertion : 

 the pressure of the air would cause the distension of the 

 larynx into a sac. 



In all the anthropoid apes the male is larger and stronger 

 than the female, with larger canine teeth. In the Orang 



