10 U. S. BUREAU OF FISHERIES. 
The generalization that the high death rate in pike-perch eggs is 
due to lack of impregnation thus seems to be unwarranted. That the 
present methods of preventing cohesion of the eggs are responsible 
for a certain percentage of the mortality is probable, but they do not 
account for all the loss. On the other hand, it has been shown that 
about 25 to 30 per cent of representative samples of 29-hour eggs show 
abnormalities that must lead to either malformation or death. If an 
average loss is then considered as 50 to 60 per cent (and that is a fair 
estimate), about half of this is due to the agency which manifests 
itself in abnormal development. This cause is in all probability to 
be found in the practice of retaining captured fishes in pens for the 
purpose of permitting eggs and sperms to mature. 
