147 



These ilLastritioas clearly point to an unJerlying princi- 

 ple. Tne orgiinizHtion of the brain is the expresision of the 

 adjust-nent «hich has constantly taken place betvjeen the race 

 of animals and the stimuli to which thay have been subjeutei. 

 This relationship between nervous organization and peculiari- 

 ties in the anvironment is such a close one that the degree of 

 developTient of the several parts of the brain may be very une- 

 qual indeed. And hence it is that the cerebellati of Mustelus 

 is so highly organized, for this is the correlative of the po/r- 

 erful swimning capacity of the animal, requiring an adequate 

 mechanism of equilibration. The forebrain, with its luxurious 

 development of neurones, nas arisen in connection with the 

 large place occupied by olfactory impressions in the Selachii. 



Worphological data in neurology must necessarily provide 

 the foundation for all physiological /rork, but it is none the 

 less important that morphological facts should have the check 

 of experimental evidence /fherever this is possible. Nowhere is 

 there to-day a more urgent need for careful observations of this 

 character than in the group of the fishes, where nervous proc- 

 esses are of such a simple order as to introduce relatively 

 few complications. Thorndike ( '99) has made at least a begin- 

 ning in this field for the teleosts. This observer placed a 

 screen with but one opening across the course in which Fundulus 

 desired to swim. He found that after several repetitions the 

 animal "learned to get out". Here, it would seem, there was a 

 trie memory of previous activities in the absence of any nervous 



