98 Herbert Eugene Walter 



or again into responses which are characteristic of only one species 

 of a genus and not necessarily of other species of the same genus, 

 and, finally, into those peculiar to the individual as such, which 

 may not in all particulars be shared by other representatives of 

 the species to which the individual in question belongs. It is in 

 this sense of the terms generic, specific and individual, that behav- 

 ior will be taken up in the present section. 



A Generic and Specific Behavior 



In the present inquiry a basis for generic comparisons is afforded 

 by a study of the behavior of individuals of four different genera, 

 namely, Planaria, Dendrocoelum, Phagocata and Bdelloura, while 

 some idea of specific differences is made possible by compar- 

 mg the behavior of individuals of the two species Planaria macu- 

 lata and Planaria gonocephala. In the cases of Dendrocoelum, 

 Phagocata and Bdelloura it is obvious that the conclusions drawn 

 are based in each instance upon the behavior of representatives of 

 a single species under each genus. The question may be properly 

 raised as to how .far such conclusions indicate generic behavior 

 and how far specific behavior. Conceding that from the data 

 obtained exact deductions may not be drawn, the fact still remains 

 that the three species, Dendrocoelum lacteum, Phagocata gracilis, 

 and Bdelloura Candida, are separated from each other by generic 

 gaps, such that the differences exhibited by these species may be 

 regarded as generic in degree. The point unestablished, then, is 

 whether other species of the genera in question if examined might 

 not show that the behavior, which in these single representative 

 species seems generic in nature, is not characteristic of other species 

 of the same genus as well. 



It will be convenient to present the data of both generic and 

 specific behavior at the same time. 



Percentage of Negativeness. The manner of obtaining this 

 criterion of behavior has been explained in the section on 

 Phototaxis (p. 72). It will be remembered, too, that in Table 

 XII a comparison was made between positive and negative worms, 

 showing the degree of their orientation to directive light. The 



