MAMMALIA. 



543 



perfectly adapted for its marine life. It is essentially 

 gregarious, living in herds or " schools," and haunts the 

 pelagic water, /.^., at or near the surface of the open sea, 

 though not usually found far from land. Along with the 

 rest of the Cetacea^ it was for long regarded as a fish till the 

 researches of Cuvier revealed its true relationships. 



The diet of the porpoise is fish, the pelagic species, 

 such as mackerel, herrings and pilchards, being the usual 

 victims. 



Fig. 374.— The Common Porpoise {Phoccena communis). 

 (From Flower and Lyddeker.) 



Passing to the internal characters we note the absence, 

 or practical absence, of salivary glands. The primary 

 function of lacrymal glands is to supply moisture for the 

 surface of the eye, that of the salivary glands to supply 

 moisture to the food : hence the absence of both in aquatic 

 animals. Under the tough skin we find a very dense thick 

 layer of fatty tissue or ''blubber," which is really the 

 enormously hypertrophied panniculus adiposus. The por- 

 poise has dispensed with its outer coating of hair to 

 produce less friction and consequently greater speed, hence 

 the warmth of the body is retained by "blubber." 



