XX11 GIANT FISHES, WHALES AND DOLPHINS 



genital aperture, the other the vent or anus. It is possible 

 to distinguish the sex by the distance between the two aper- 

 tures, these being closely approximated in the female and 

 farther apart in the male. There is a modification in these 

 aquatic mammals of the normal manner of suckling the young, 

 necessitated by the environment in which they live. The 

 mammary glands have large sinuses or reservoirs, in which 

 the milk collects, and which, by the contraction of certain 

 body muscles, are forcibly emptied by way of the teat into the 

 mouth of the young, so that the whole process of feeding is 

 greatly accelerated. 



