References 195 



The energy evolved as a consequence of stimulation 

 may be employed mainly in producing structural 

 modifications of the cell substance, or it may be ex- 

 pended mainly in producing motor reactions. The 

 response is usually purposive and social in either 

 case. 



Zur Strassen in a discussion of "Animal Behavior 

 and Development" before the Seventh International 

 Zoological Congress at Boston called attention to 

 the social behavior of cells and the analogies be- 

 tween such behavior and the activities of social in- 

 sects. The comparison is suggestive, but as Zur 

 Strassen points out, there is a closer relationship be- 

 tween the cells of the metazoan body and the pro- 

 tozoa, which are not improbably the direct ances- 

 tors of these cells. Were the protozoa social in 

 their behavior, did the different behavior of the 

 several castes depend upon mutual interaction as it 

 does to a certain degree among social insects, the 

 analogy between behavior and development would 

 indeed be close. 



REFERENCES 



ALLEN, B. M. The origin of the sex cells of 

 Amia and Lepidosteus. Jour. Morph. 22, i, 1911. 



HARRISON, R. G. The outgrowth of the nerve 

 fiber as a mode of protoplasmic movement. Jour. 

 Exp. Zool. 9, 787, 1910. 



HOLMES, S. J. ( i ) Observations on isolated liv- 



