RISKS OF OVA IN HATCHING. 177 



In the artificial mode of breeding, when I 

 have obtained ova from living fish, under water, 

 and added to them milt in its milk-like state 

 also from living fish, and expressed under water 

 a certain number, and only a certain num- 

 ber, of these ova have become impregnated, 

 and have been hatched ; of the remainder, 

 some have become opaque almost immediately 

 from the absorption of water ; and some, the 

 larger proportion, have retained their trans- 

 parency for a variable time ; many of them 

 more than a month. Why a portion should 

 receive into their interior the spermatozoon, the 

 impregnating particle, why others should so 

 soon absorb water, and by the congelation of 

 the yolk become opaque ; and why another 

 portion should resist so long the entrance of 

 water without progressive development, at 

 present, I believe, can only be conjectured. 

 Next, of the impregnated ova : these, if carefully 

 examined will be found to vary in size *; to be 



* Of twelve mature ova of a salmon from the Dee, 

 the heaviest weighed one grain and eight-tenths, the 

 lightest one grain and two-tenths of a grain. The ova 

 of the charr I have found to vary in diameter, from 

 sixteen to twenty hundredths of an inch, and in weight 

 from one grain to seven-tenths of a grain. 



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