104 Studies in Animal Behavior 



found by Miss Towle in the ostracod crustacean 

 Cypridopsis. Ordinarily negative, this form could 

 be rendered positive by being picked up by a pipette 

 and dropped out again. Often specimens were 

 changed from negative to positive when they col- 

 lided with the side of the dish. In an allied form, 

 Cypris, Yerkes observed similar changes. Parker, 

 on the other hand, found that in the copepod Labi- 

 docera positive specimens could be rendered nega- 

 tive by handling them with a pipette. 



The influence of contact on the phototaxis of Ran- 

 atra is very marked. Handling this insect throws 

 it into a death feint which inhibits at first all photo- 

 tactic response, but soon after the creature begins 

 to rouse itself and slowly walk about, it frequently 

 manifests a tendency to slink away from the light. 

 On further exposure this tendency is superseded by 

 the positive response which becomes more decided 

 until the creature is wrought up to a pitch of frantic 

 excitement. Reversal by contact is very clearly 

 shown by this Insect if when it Is swimming toward 

 the light It Is seized and gently stroked, or simply 

 picked up by the tip of the breathing tube and 

 dropped back again into the water. Curiously enough 

 Ranatra does not feign death while in the water, or 

 at least it does not give more than a momentary 

 suggestion of such a performance, but the stimuli 

 which would at once cause it to feign death when In 

 the air, produce an immediate reversal of its photo- 

 taxis while in the water, 



