284 CHAS. W. HARGITT. 



Of the species which have come under my own observations as 

 light-perceptive, two are tube-dwelling, and one free-living, but 

 secreting itself under various forms of cover, or occasionally bur- 

 rowing in sand. Certainly neither geotropism nor stereotropism are 

 equally or reasonably applicable as explanations of all these 

 varied conditions and habits. I believe we are therefore forced to 

 the conclusion that physiological conditions of adaptation are 

 primarily involved, and that the various phases of behavior are so 

 many expressions of such adjustments. 



SYRACUSE UNIVERSITY, 

 January I, 1907. 



