378 V. \V. GAMBLE AND FREDERICK KEEBLE. 



spectroscope scale). The green screens were made (1) of three 

 layers of Baker's green gelatine, which transmits green and 

 a trace of extreme red 0—0-5; (2) of a double glass cell, oue 

 compartment of which contained ammoniated copper sulphate, 

 the other potassium bichromate of such strengths as to 

 transmit only green and a narrow band of extreme red — 0"5. 

 The blue screen contained ammoniated copper sulphate, which 

 transmits some green and all the blue violet. The experiment 

 was made in the open. 



Experiment I. — Started 12 a.m. September 2nd. 

 Recorded 2 p.m. 



Red Screen. — All gave starch reaction. 



Grreen-blue screen. — All gave starch reaction. 



Red-green screen. — All gave starch reaction. 



White light. — All gave starch reaction. 



Control in darkness. — All gave no starch reaction. 



Experiment II. — For this purpose adult Con voluta were 

 used. They had been kept in the dark from August 20th to 

 September 2nd, and had become completely free from starch. 

 The same screens were used as for Experiment I. Experiment 

 lasted from 10 to 12 a.m. September ord. The vessels were 

 placed in the open. Direct sunlight was used. 



1. Under red screen. — Cousiderable amount of starch. 



2. Under green screen. — No starch. 



3. Under KoCrO^ screen (= red to green). — Much starch. 



4. Under blue screen. — Fair amount. 



5. Under white light. — Much starch. 



Slight starch reaction obtained after five minutes' exposure 

 to bright sun, and a very distinct reaction after fifteen minutes' 

 exposure to diffuse light. 



Section III. — The Development of the Green Cells. 



1. The Occurrence and Significance of Chlorophyll 



in Animals. 



Chlorophyll is known to occur in animals under three 

 distinct forms : (1) as the chromatophores of the green 



