PLATE 10 



EXPLANATION OF FIGURES 



Views of specimen no. 8: a, after four days on material shown; h, in jar having 

 black bottom, and transparent walls, surrounded by gravel (after seven days); 

 c, in jar having black walls and transparent bottom, with gravel underneath (after 

 ten days); d, taken on a black bottom, immediately after transfer from a white- 

 bottomed, black-walled jar, in which the fish had remained 9 days. 



498 



