2 U. S. BUREAU OF FISHERIES. 
harmful, and a certain amount of loss is probably due to them. 
Reighard (1890) found that by very careful handling of the eggs at 
and immediately after fertilization the percentage of eggs that 
started segmentation soon after fertilization could be considerably 
increased. Describing the loss met with in the ordinary course of 
the routine methods, he states that in 252 samples examined 11 per 
cent had died due to lack of impregnation and 33 per cent due to 
injury. Unfortunately, although he designates the day and hour 
at which these observations were made, the age of the eggs is not 
specifically given. From the context it would appear as 29 hours. 
It seems that an egg was designated as dead when it showed an 
opaque white color, a criterion which was adopted also in the present 
investigation. ; 
The figures of the losses in ordinary handling of pike-perch eggs 
iven by Reighard are somewhat at variance with those gneu by 
a H. Almy in some unpublished notes on the pike perch. His find- 
ings and those of the authors follow: 
Almy. Schrader and Schrader 
Age of eggs. Sew ' Age of eggs. mere 
2.5 05 
5.4 | 4 hours 30 minutes. . 10 
&1 || 8 hours 15 minutes... Ded 
12.6 || 19 hours............. 4.3 
S158 29 ROUPS Sco cieeot ceiantreeiaenimina sigtwty ain 5.0 
35.5 |} 2 days. &3 
39, 0 || 3 days 13.3 
33.4 | 4 days ee 33.2 
j DOA Y Saye Boo Ssleioizqaiaieyssste a Wactaawe Seiea ease 37.1 
It will be seen that in contrast to the 33 per cent of white eggs 
given by Reighard, Almy observed only 5.4 per cent at 27 hours, 
while our own observations are lower still. Almy’s and our figures 
agree fairly well, the latter being lower up to two days and a trifle 
higher at four days. It is not quite clear to what such a discrepancy 
could be due, although Reighard’s hypothesis of injury as a cause 
of mortality would, of course, itself allow for large differences on 
account of the varying skill and care bestowed on the eggs. (Tem- 
perature conditions were in all cases apparently the same, the water: 
being in the neighborhood of 45° F.) Reighard describes the in- 
jury as taking place most easily over the oil globule, and there is 
no reason to dispute the observation. However, the following ex- 
planation which he advances to account for this phenomenon does 
not seem to rest on a very firm physical basis (Reighard, 1890, pp. 
33, 84) : 
In the natural position the yolk sphere lies with its lower half against the 
egg membranes. These membranes, therefore, support this half of the yolk,. 
surrounding it as if it were resting at the bottom of a cup. The upper half 
of the yolk is, on the contrary, not of the same form as the investing membrane; 
its spherical surface is interrupted by the protruding oil globule. 
The result of this arrangement is that when any pressure is brought to bear 
on the egg membranes, so that the space within which the yolk lies is reduced, 
the yolk is able to resis. this pressure by fitting itself against the egg mem- 
brane at every part of its surface except over the oil globule, The strain, 
