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 ou 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 cause 
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 changed 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 auy 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. 
