394 F. W. GAMBLE AND FREDERICK KEEBLE. 



of clilorophyll in the developing green cells, we attempted 

 to investigate the action of monochromatic light. For this 

 purpose larva) from the vessel A used in the preceding 

 experiment were employed. They were placed under screens 

 transmitting red, green, and blue light respectively. The 

 result of three successive days' exposure to filtered sunlight 

 showed that the colourless cells of the larvae were the most 

 developed in green light, agreeing with those exposed to 

 white light; those in the blue light had remained stationary; 

 and those in the red light were in an intermediate condition. 

 None of these cells had become green, whereas larvae hatched 

 from comparable batches of eggs placed in the light had in 

 the same interval of time become distinctly green. 



We conclude that a high light-intensity is favourable, and 

 that darkness is inimical, to the formation of chlorophyll in 

 developing green cells. But inasmuch as the infecting 

 organism when ingested is now at one stage and now at 

 another stage of development, the influence of light is not 

 regular. It may call forth the development of chlorophyll 

 with extraordinary rapidity, or it may induce it but very 

 slowly. 



Section IV. — The Tkopisms of Convoluta. 



Geddes has shown that Convoluta is positively photo- 

 tropic. Left to themselves in a jar of water laterally illu- 

 minated, the animals mass themselves up on the brighter 

 side. Haberlandt has demonstrated that the rising up of 

 Convoluta to the surface of sand or water, which occurs 

 when the containing vessel is perfectly still, is a negative 

 geotropism, and not a movement toward oxygen. He also 

 showed that extremely slight vibration is snflicient to inhibit 

 the negative geotropic reaction, and to cause the animals to 

 collect at the bottom of the vessel in which they are kept. 



The object of this paper, the investigation of the bionomics 

 of Convoluta, required of us to examine somewhat more 

 closely into these tropisms in order that we might discover 



