178 



S. O. MAST 



Fig. 10 Diagram representing the process of photic orientation in Ama- 

 roucium tadpoles. I, I, horizontal beam of light; 1 to 6, different positions of 

 tadpoles. In position {2) the retina is fully exposed, but as the tadpole reaches 

 position (S) it becomes shaded, owing to the rotation on the longitudinal axis. 

 This causes the tail to bend toward the ocular side, which, owing to rapid rotations, 



