4 U. §. BUREAU OF FISHERIES. 
even 8 hours 15 minutes. Most of the unsegmented eggs at the 
latter stages on being examined cytologically appeared to be normal. 
They were therefore merely lagging behind. The proportion of 
eggs which has failed to cleave becomes progressively less with age. 
which in itself supports the idea that we are dealing here rather with 
a delay in cleavage than with a lack of impregnation. The curve 
in figure 1 (p. 3) shows graphically the numerical conditions en- 
countered. These data are emphasized here merely to show that it is 
manifestly impossible even after eight hours to designate eggs as un- 
fertilized when the absence of segmentation is taken as a criterion. 
Fics. 2 to 10.—Surface views of pike-perch eggs. Magnification, approximately x 100. 
Fic. 2.—Normal* 6-hour +-celled blastoderm. Fig. 7.—Abnormal 19-hour blastoderm, 
Fic. 3.—Normal 19-hour blastoderm. Fie, 8.—Abnormal 19-hour blastoderm. 
Fic. 4.—Abnormal 8-hour blastoderm. Fic. 9.—Abnormal 29-hour blastoderm. 
Fic. 5.—Abnormal 10-hour blastoderm. Fic. 10.—Abnormal] 29-hour blastoderm. 
Fic. 6.—Abnormal 10-hour blastoderm. 
In addition to all this it must be considered that in the artificial 
insemination of the pike perch the eggs are immersed in milt which 
is diluted very little. The chance of a normal ripe egg remaining 
unfertilized must therefore be extremely small, and, as a matter of 
fact, it is surprising that polyspermy is not more often encountered. 
In addition to the eggs which are found to be dead almost imme- 
diately, and to those which are slow to cleave, there is a third class 
which has been designated as “abnormal.” In explanation it must 
be stated that minor irregularities in cleavage are not necessarily an 
indication of pathological conditions (H. V. Wilson, 1891), and only 
such extreme cases as are shown in figures 4 to 10 were rated as 
