86 



The large size of both the ear and the cerebellurn of Mas- 

 telus is to be explained by the swimming habits of the animal. 

 The structures have an equilibr^tory value. 



The cerebellum has apparently arisen in the phylogeny of 

 vertebrates as a fusel outgrowth of the pair of tubercula acus- 

 tica, a specialization of that part of the oblongata forming 

 the original terminal station for the acustico-lateral system. 



