158 AMERICAN FISH CULTURE. 



ovary has its parallel in the turtle, and possibly in all of 

 the vertebrata. 



" It is scarcely necessary to add that the microscope 

 shows other and smaller ovarian eggs. An ovary of the 

 size above mentioned contains about 70,000 ova, ready to 

 be laid. Their diameter increases, as soon as they are put 

 in water and impregnated, from T 5 to J^ of an inch. 

 This is by the endosmosis of water between the yolk and 

 the shell membrane.* Of the embryonic development, we 

 have, as yet, only an imperfect outline to present. Forty- 

 one hours after impregnation, the condition of the embryo 

 is, on the whole, in advance of that of coregonus on the 

 thirty-third day. The under surface, from the nose to the 

 beginning of the ventral, is in close contact with the yolk, 

 which is composed of a great number of rounded divisions, 

 such as are seen in the complete segmentation of that 

 body, while its surface is necked with pigment stars; of 

 which a less number may be distinguished on the forward 

 part of the trunk. That part of the embryo which swings 

 free makes a spiral half turn, so that the dorsal fin is 

 turned toward, instead of from, the yolk-sac. The head, 

 which is pointed in front, and flattened, bears no resem- 

 blace to that of the grown animal, and it would be, perhaps, 

 fanciful to compare it even to such forms as Petromyzon 

 (Lamprey eel.) A large portion of it is occupied by the 



* The same takes place in a less degree in the egg of Coregonus 

 (white fish.) (Carl Vogt, loc. cit. p. 27, PI. I. fig. 9.) Accus- 

 tomed only to eggs of trout, Green was much astonished to behold 

 the mass of ova swell to near twice its first bulk. 



