NOTES ON THE INCREASE IN SIZE OF FISH 

 OVA AFTER WATER HARDENING 



B^' Ward T. Bower, 



r. S. BUREAU OF FISHERIES, WASHINGTON, D. C. 



As the result of a privilet^e extended to me to draw upon 

 the records of the Bureau of l^^isheries, it has l)ecome possil)le 

 to bring- to your attention for the sake of comparison and 

 analysis observations made from time to time during- the past 

 few years by several of the Bureau's station superintendents 

 with reference t(T increases in the size of fish o\-a during the 

 period of incubation. The object in subn-iitting these data 

 is to point out the advisabilit}- or even necessity of such con- 

 siderations, and at the same time to stimulate further inves- 

 tigation of the subject. 



The expansion of fish eggs during water hardening is of 

 no particular concern to the fish culturist as regards \-olume 

 other than that receptacles of sufficient capacity be provided. 

 1'his absorptive period coincides with the adhesive stage, 

 covering the early processes of segmentation, when the eggs 

 are extremely sensitive and should not be handled. It is 

 when this sensitive period is past, and at the time they are 

 read}' to place in the hatching e(|uipment, that measurement 

 becomes a matter of importance. Bleretofore it lias been 

 generally considered that from this stage of development 

 there was little or no further increase in size throughout the 

 ])eriod of incubation. 



The prevalence of this erroneous idea is ratlier strikingK- 

 e\-ident from the fact that fish culturists in computing llie 

 losses, the output of eggs, and the nuniber of fr}- hatched, 

 ha\e not until recently taken into consideration, or at least 

 made any allowance for, an increase. This was all in fa\-or 

 of the fish culturist's record, but lacked accuracy, as the 

 out put of fish was frequently determined b\- a \-olume meas- 



