BEHAVIOR UNDER NATURAL CONDITIONS 187 



and night, that they succeed in providing themselves with sustenance. 

 Wlien prey abounds, the collisions are frequent, their quest profitable, 

 and sustenance easy; when scarce, the encounters are correspondingly 

 less frequent, the animal fasts and keeps his Lent. The Lagynus 

 crassicoUis, accordingly, never sees its victim from a distance and in no 

 case directs its movements more toward one object of prey than toward 

 another. It roams about at random, now to the right and now to the 

 left, impelled merely by its predatory instinct — an instinct developed 

 by its peculiar organic construction, which dooms it to this incessant 

 vagrancy to satisfy the requirements of alimentation." 



It is evident that these words of Maupas are an excellent description 

 of behavior based on the general method of trial of all sorts of conditions 

 though varied movements, and they bring out clearly the essential prin- 

 ciples in the food reactions of infusoria. The same method of behavior 

 is found, as we have seen, throughout almost the whole circle of activi- 

 ties in these organisms ; the food reactions epitomize the entire behavior. 



LITERATURE X 



A. Modifiability of behavior in infusoria : Jennings, 1902, 1904 d; Hodge and 

 AiKiNS, 1895. 



B. Food habits of infusoria: Maupas, in Binet, 1889; Balbiani, 1873. 



