1917] Estrrh/: Specificity in Behavior 389 



be given here, thougli it is outside tlie field of this particular paper. 

 It has been found from many trials that A. touaa, if taken from the 

 surface, is predominatingly negative to gravity in diffuse light, and 

 positive, for the most part, in the dark ; and that an animal will 

 swim up toward a light at the top and down toward a light at the 

 bottom. But animals from bcdoiv the surface are positive to gravity 

 in diffuse light, and swim down from a light at the top. 



It has been shown that Acartiae taken from below the surface do 

 not react to light, if tested at once, as they do after several hours, 

 or as surface animals always do. For the sake of discussion we may 

 say that, so far as collecting shows, the eopepods caught at ten fathoms 

 are negative to light and positive to gravity, and that surface animals 

 are positive to such intensity of light as exists at the time, and nega- 

 tive to gravity. Such, in fact, appears to be the case from experi- 

 mental evidence, but we should not discover it to be so if we use 

 only surface animals or those from below the surface that have been 

 in the laboratory too long. Even admitting, furthermore, that the 

 essential features of responses as related to habits can be satisfactorily 

 worked out in the laboratory alone, it is necessary to use animals 

 from different habitats and before the corresponding physiological 

 state has changed. In addition, as Ritter (1916, especially p. 461) 

 has set forth in a more general way, different species show diversities 

 in other regards than structure, and this must be taken into account 

 in general explanations of habits based on experiment. 



