NATIONAL FISHERY CONGRESS. 319 



Twins and double-headed mousters, common with trout, are so rare with the 

 whitefish that I have discovered but few, except in the case of the eggs of a single 

 fish, where they amounted to over 10 per cent of the whole. 



Next come aneurisms and ruptured blood-vessels, probably between 6 and 7 per 

 cent. Aneurisms are much more common than ruptures, and, contrary to the rule 

 with the higher animals, they cause death without the complete rupture of the artery. 

 The red corpuscles form a clot in the enlargement, the serum filtering through the 

 mass, and only a straggling red corpuscle being seen here and there coursing through 

 the vessels of the body. The clot seems to collect them all. The heart beats feebly, 

 and death ensues. Aneurisms are most common in the side of the embryo about the 

 middle of the body, and it seems that most of them are on the right side. 



In the earlier stages, that is, up to about two months from the taking of the egg, 

 there is a small loss occasioned by the rupture of the yolk sac. In these cases the 

 embryo generally lives a few days after the rupture. I have not computed this loss 

 very closely, but it does not probably exceed 1 or 2 per cent. 



In all these cases, where the embryo is far enough advanced to show the pigment 

 cells, or "color stars," and is approaching death, the branches of the cells become 

 shortened, and usually at death only the nucleus remains. 



For the remainder, I have not been able to determine what is the cause of death. 

 In many cases 1 find what seem to be small patches of a fungoid growth on the body 

 of the embryo. I can not see that they do any harm, and have not discovered them 

 on the bodies of dying embryos more than those in an apparently healthy condition. 



It seems to me that these deaths are the result of the natural weeding out of the 

 weakly individuals, "the survival of the fittest," the same as in the higher forms of 

 life, and that no amount of care on the part of the tish-culturist can prevent it, except, 

 possibly, in reducing the number of abnormalities by exercising great care in the 

 taking and handling of the eggs, eminent biologists holding that monstrosities are 

 often caused by injuries sustained at certain stages in the development of the individual. 



In this connection I would state that, so far as my observation goes, this loss of 

 eggs after the embryo is formed varies greatly from year to year. It is also certain 

 that eggs taken near the close of the season suffer a greater loss in this respect than 

 those taken at the flood. With eggs taken near the close in small lots this loss may 

 amount to a fourth of the whole, or even more. 



PUT-IN BAY, OHIO. 



