256 A. M. Banta 



apathy was often somewhat overcome by use of the glass ring 

 already mentioned. The ring served to retain the animals in the 

 center of the tank until settled, so that their movements could be 

 readily interpreted with reference to the light effect, and at the 

 same time by its removal the animals were more or less disturbed 

 mechanically. Once roused from their inactive state, they re- 

 sponded more quickly in a directive way than they would have 

 done if influenced by light alone. The mechanical stimulation 

 produced by lifting the ring lasted only a second and was wholly 

 non-directive. Secondly, the animals, if not yet settled after being 

 transferred to the tank, responded to other stimuli (thigmotactic, 

 etc.), which were powerful though non-directive in effe'ct, so 

 strongly that the directive influence of the light was not at once 

 observable. After a time these non-directive stimuli became less 

 influential in their effects, and the light with its directive influence 

 became the effective stimulus. Thirdly, the photokinetic response 

 to light tended for a time to mask the phototactic response. 



The first eft'ect of light of moderate and high intensities was 

 often largely photokinetic, some of the animals starting up quickly 

 very much as when mechanically stimulated. Sometimes, if the 

 animals were already pretty thoroughly settled in the tank, no 

 movements would occur for from 2 to 5 minutes, but usually after 

 a period of 2 to 20 minutes, if the illumination were strong, a 

 fairly general activity commenced. This activity, however, did 

 not always manifest itelf at first as a directive response to fight 

 stimulation. The directive response, as indicated by the positions 

 of the animals in the tank, ordinarily did not appear before an 

 exposure varying from 15 to 90 minutes. 



Observations of individual animals, however, brought out the 

 fact that very often the phototactic response on the part of each 

 individual occured rather quickly; but the animals on reaching the 

 negative end of the tank recoiled from it and wandered the greater 

 part or all the way back to the opposite end of the tank. This 

 wandering about tended to obscure the directive reaction until, 

 after a time, the animals became more or less settled. It was then 

 that the directive response became most marked, for the animals 

 came to rest in regions near the negative end, and often half, or 



