ACTIVITIES OF THE AMAROUCIUM TADPOLE 247 



In order to determine the character and definiteness of the 

 response of the Amaroiicium tadpole to gravity, a number of 

 experiments were carried out, in each of which a large number of 

 tadpoles, collected and used as soon as possible after their emer- 

 gence from the parent colonies, were placed during their free- 

 swimming and attachment periods in a glass cylinder contain- 

 ing a column of water 5.5 cm. in diameter and 40 cm. in depth, 

 note being made of the levels at which the tadpoles became 

 attached. 



The results of twelve of these experiments are shown in table 

 1. The special conditions under which each experiment was 

 made are stated in the explanation of the table. 



While these experiments were designed primarily for the 

 study of the response of tadpoles to gravity, those numbered from 

 1 to 6 in the table show also the effect upon this response of 

 special or unusual conditions of light, and the experiment num- 

 bered 12 shows the effect of the absence of light in modifying the 

 normal geotropic response. 



Five of the experiments, those numbered from 7 to 11 in the 

 table, were made under conditions considered as nearly normal 

 as it is possible to make them in the laboratory. The unjack- 

 eted clear glass cylinder stood 2 feet directly in front of a north 

 window on a table the top of which was 5| feet below the top 

 of the window and 8 inches below the window sill. The rays of 

 light entered the column of water more or less obliquely from 

 the general direction of the window and were therefore some- 

 what directive. Combining and summarizing the results of 

 these experiments, it is found that 77.6 per cent of the total 496 

 tadpoles used in the experiments became attached either to the 

 bottom or to the edge of the bottom on the least illuminated 

 side of the cylinder; 9 per cent to the side below the middle; 

 7.6 per cent to the side above the middle; 3 per cent to the side 

 of the cylinder at the edge of the water surface, and 2.6 per cent 

 remained floating on the surface of the water, perhaps attached 

 to or held by the surface film. 



Notes made during the course of one of the experiments will 

 serve to show the nature of the activities observed: 



