APPENDIX 



In all cetaceans the facial portion of the skull is greatly 

 elongated, and especially in the Mystacoceti the mouth is 

 exceedingly large to accommodate the baleen, which hangs 

 in two parallel rows from the upper jaw. Probably no 

 mammalian adaptation for the securing of food is more re- 

 markable than the whale's baleen. It is almost unbelievable 

 that an animal which once had teeth could, as its food 

 changed, replace them by a complicated straining apparatus 

 such as the whalebone. The baleen is an epidermal growth 

 and is in reality merely an exaggeration of the transverse 

 ridges present in the mouths of land mammals. 



We know that the Mystacoceti at one time had teeth, for 

 in foetal whales two sets of minute teeth are present under 

 the skin, corresponding to the "milk" and "permanent" den- 

 tition of ordinary mammals, but these disappear before the 

 baleen begins to develop. 



Another interesting feeding adaptation is present in the 

 throat of the whale. The nostrils, instead of opening into the 

 back of the mouth, as in land mammals, are directly con- 

 nected with the lungs by a prolongation of the "wind-pipe" 

 called the epiglottis, which entirely shuts off the whale's 

 breathing passage from the mouth. Thus the animal can 

 swallow its food beneath the surface without danger of 

 strangulation through getting water into its lungs. 



When whales lived upon the land external ears were neces- 

 sary, but as they became completely aquatic such "sound col- 

 lectors" were not only of no more use but highly undesir- 

 able, because, like the useless hind-limbs, they offered addi- 

 tional resistance to the water; therefore the external ears 

 were lost, but their muscles still remain about the minute 

 ear-orifices of the present-day Cetacea. 



The internal modifications which the whales underwent 

 as they assumed an aquatic existence are fully as remark- 

 able as the external changes. In the section on osteology 

 it has been explained how, in living cetaceans, the entire 

 skeleton is loosely articulated so that great flexibility and 

 freedom of movement is given to the body, how the neck 



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