3i8 Journal of Comparative Neurology and Psychology. 



served. The promptitude and decision of its negative move- 

 ments may increase up to a certain point if the insect is kept 

 close to the light, but when the movements begin to become 

 vigorous there is a transition to the positive type of reaction. 

 Often the advent of positive phototaxis is accompanied by a 

 marked accession of energy as if a strong dormant propensity 

 had suddenly been awakened. 



The causes that produce the negative reaction are, as a 

 rule, those which lead to diminished activity and excitement. 

 Cold, exposure to darkness, the quieting effect of contact stimuli 

 lead to a condition of lessened excitability and, perhaps as a 

 result of this, to a negative reaction to light. 



^. Head and Szvaying Movejnents in Negative Phototaxis. 

 It would naturally be expected that the leg movements in nega- 

 tive specimens are the reverse of those in positive ones, and to 

 a certain extent this is true. It was thought not improbable 

 that the movements of the head would be reversed as well ; but 

 it was found that in all cases in which Ranatras moved away 

 from the light the head reflexes take place exactly as in individ- 

 uals that are positive. Both in strong and in weak light, under 

 a variety of different conditions the head reflexes are the same 

 in kind regardless of the general sense of the response. 



The swaying movements in negative phototaxis are readily 

 observed in Ranatras that have been resting quietly in the dark 

 for some time in a glass dish of water. If an incandescent light 

 be brought near them they are at first irresponsive. By moving 

 the light slowly about them the head reflexes are first induced. 

 Then there may be very slow and at first scarcely perceptible 

 movements of the legs, the second and third pairs being very 

 lazily extended on the side towards the light, and flexed on the 

 opposite side, the back being rolled over so that it more nearly 

 faces the light. On placing the light on the opposite side of 

 the body there is a very gradual extension of the legs previously 

 flexed and a flexion of those previously extended, the body 

 rolling over at the same time so that its dorsal surface lies more 

 nearly at right angles to the rays. The animal may be made 

 to repeat this performance many times in succession. After a 



