42 MARINE AND AQUATIC TRESPASSERS. 



the other's teeth. Both are encased in blubber, but in 

 the Greenland Whale this coating is very much thicker 

 than in the Spermaceti Whale. The reason is simply 

 this, that the seas in which the former animal lives are 

 colder than those of the southern seas, and that, there- 

 fore, it must be protected by a thicker blanket of non- 

 conducting material. 



