NATURAL HISTORY STUDIES 



separated bony fishes, where there is no egg-shell, 

 but only a firm shell-membrane. Both in the trout 

 and in the gold-fish the single-celled glands 

 of the embryo's skin secrete before hatching a 

 fluid which has a digestive action on the shell- 

 membrane. This becomes delicate and finally 

 almost like wet paper, readily allowing the escape 

 of the miniature fish. 



