ACTIVITIES OF THE AMAROUCIUM TADPOLE 249 



September 12, 1917. 4.45 p.m. All tadpoles liberated by an 

 Amaroucium colony during a fifteen-minute interval, seventy-five in 

 number, collected in a glass cylinder and placed upright on a table 

 before a north window. All tadpoles swimming actively at the surface 

 of the water. A tadpole dives downward now and then to a depth 

 of 2 to 3 cm., but returns immediately to the surface. 



4.53 P.M. One tadpole dived to a depth of 6 cm. and then returned 

 to the surface. Others do the same. None diving deeper. 



4.55 P.M. One tadpole swam straight down to a depth of 32 cm., 

 stopped swimming, turned tail upward, and slowly sank to the bottom, 

 where it remained motionless. 



4.58 P.M. One tadpole descended to a depth of 9 cm., came in con- 

 tact with the side of the cylinder and became attached, not able to 

 free itseK by repeated attempts to swim away. 



5.01 P.M. One tadpole swam' half way to the bottom, turned and 

 swam to the top. 



5.03 P.M. Several tadpoles dived to depths of about 15 cm., all but 

 one returning to the top, one sank motionless to the bottom. 



5.08 P.M. Several tadpoles swimming about actively at and near 

 the bottom, others at the top and in the upper strata of water, one 

 sinking motionless with metamorphic changes taking place. 



5.13 P.M. Several tadpoles swimming at various depths between 

 the top and bottom. 



EXPLANATIONS, TABLE 1 



*SF,, attached to surface film (floating); SE, attached at line in which water 

 surface and side of cylinder meet; BE, attached along the bottom edge; B, at- 

 tached to the bottom; figures in the columns indicate the number of tadpoles 

 attached at various levels; figures at the bottom of the columns show the total 

 number of tadpoles used in each experiment. 



Experiments 1 and 2 made simultaneously with tadpoles taken from the same 

 colonies of ascidians. This is the case also with experiments 3 and 4 and with 

 5 and 6. 



Experiments 1 and 3 Sides and top of the cylinder covered with black paper. 

 Light from a north window reflected directly upward through the column of 

 water. 



Experiments 2 and 4 Sides and bottom of the cylinder covered with black 

 paper. Light from a north window reflected directly downward through the 

 column of water. 



Experiment 5 Same as 1 and 3, except that direct rays from the sun were 

 reflected upward through the column of water. 



Experiment 6 Same as 2 and 4, except that direct rays from the sun were 

 reflected downward through the water. 



Experiments 7 and 8 The cylinder without cover set before a north window. 



Experiments 9, 10, and 11 Same as 7 and 8, except the cylinder was inclined 

 at an angle of 45° from the perpendicular. 



Experiment 12 Cylinder placed in a dark room during the free-swimming 

 and attachment periods of the tadpoles. 



