318 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



found for holding and feeding the fry, if only for a few weeks, or until they are large 

 enough to care for themselves. Nor do we believe that such a hope is wholly illusory ? 

 for the experiments of Mr. Carl G. Thompson, of Warren, Ind., who succeeded in 

 rearing this fish from the fry in considerable numbers in comparatively small ponds 

 by feeding them on fine wheat middlings, at least gives encouragement that the 

 problem will yet be solved. It is true that experiments at feeding whitefish fry at 

 Put-in Bay the past season were not successful, but the work is new and it may yet 

 be brought to a successful termination. 



MORTALITY AMONG FISH EGGS. 



As is well known to fish-culturists, there is a considerable mortality among fish 

 eggs between the stage where the embryo is formed and the time of hatching. Can 

 this be prevented? To answer this question intelligently we must first know the 

 cause, and to this end I have carried on a series of investigations, making them as 

 thorough as I could with my very limited knowledge of the several sciences called 

 into action and the appliances at hand. 



Dead and dying eyed eggs, generally easily detected by the naked eye, were 

 examined from time to time, generally in hundred lots, and where the cause of loss 

 could be determined the results were kept in memorandum. In many cases the cau^e 

 is easily ascertained ; in other cases, with my limited knowledge, it could not be 

 determined at all. I should here state that, having no microtome, all the work was 

 done in gross, simply by the aid of the microscope, and that without doubt one 

 well versed in the work and with suitable instruments could determine the cause of 

 death in a large percentage of those where I failed. I should also state that the 

 percentages here given are not absolute, for the reason that with dead eggs consid- 

 erable numbers were in such a condition that no opinion could be arrived at, although 

 if examined a little earlier the cause might have been apparent, and in the case of 

 aneurisms and ruptured blood vessels most of them were discovered while examining 

 apparently healthy eggs, the embryo being not yet dead but dying, and the egg 

 therefore not yet so changpd as to be detected by the unassisted eye. 



By far the greater loss of the whitefish eggs in embryo, the only ones examined, 

 is caused by insufficient food supply, the yolk being undersized, and when the store 

 is exhausted the embryo dies of starvation, this occurring at all stages from the early 

 formation of the embryo up to the time .of hatching, those with very small yolks 

 dying first and others later on. Taking an average of all my data, this amounts to 

 31 per cent of the total loss of eyed eggs, but for reasons already stated this is not 

 strictly accurate, and I am of the opinion that it is too low rather than too high. 



The next greatest loss is caused by abnormal development, and here I am less 

 certain of my percentage than in the former case, for the reason that the diagnosis is 

 more difficult to the unscientific eye. It may, however, be safely stated that the loss 

 is not far from 20 per cent, and extends over the whole period of incubation up to the 

 time of hatching, and doubtless far beyond. 



In some cases there is not the semblance of an embryo, and yet life goes on up to 

 a certain stage. The cell mass spreads out over the yolk in an irregular way, perhaps 

 a brain and a heart forming with a rudimentary spinal column, while in other cases 

 the egg dies before any of the organs are discernible. I have never observed eyes in 

 any of these more imperfect ones; in fact, the eyes are among the organs first to show 

 abnormality, while crooked spines are well-nigh universal. Often one of the eyes is 

 rudimentary or missing entirely, and sometimes both. 



