STUDIES OF FERTILIZATION 379 
eight minutes, 90 per cent segmented; sixty-three minutes, 
90+ per cent segmented; sixty-nine minutes, 95+ per cent seg- 
mented; control eggs, 99 per cent segmented. (See Fig. C.) 
4. From this time on nearly all of the eggs segment after 
centrifuging until, during the anaphase and telophase of the first 
cleavage spindle, centrifuging again tends to inhibit cleavage. 
The following table (Experiment 29) gives a fairly typical 
series of results. There were twelve such experimental series 
in all, more or less complete, giving concordant results except 
that in some at the period corresponding to 29D, 90 to 98 per 
cent were so affected that they failed to segment. On either 
side of this critical period there is a decreasing susceptibility to 
such injury by centrifuging. 
EXPERIMENT 29 
September 8, 1909 
b2 ss —— = = 
TIME OF CENTRIFUGING | 
DESIGNATION | AFTER INSEMINATION PERCENTAGE SEGMENTED | REMARES 
Pi RC a rere Control (not centri-| 100 per cent 
fuged) 
29A.......2.....| Before insemination| 100 per cent practi- 
| cally 
BOB coe we eee | 20 minutes Majority Eggs matted loosely 
DAA Ok sole aed te | 30 minutes Majority 
DO a teens caer | 41 minutes 20 to 30 per cent 
PA) Dine cee eae | 51 minutes 70 to 80 per cent 
Pe) Disa cs Seno et OL 66 minutes 90 to 95 per cent 
DOG a ee wet nee 79 minutes 100 per cent 
NTs, wes thenuas chs 95 minutes 100 per cent 
20) Roane Ae eee 114 minutes 100 per cent 
7A08 jas 6 Sale ae 121 minutes Some unsegmented 
ot eas eh 127 minutes Less than majority} Centrifuged during 
and these irregu-| process of Ist 
| lar cleavage 
At) Cy ee ae | 149 minutes | Most segmented fur-| Centrifuged in 2-cell 
ther | stage 
| 
Two major processes are going on in the egg at this time, 
viz.: maturation and fertilization. The injury is not primarily 
to the process of maturation, for the eggs that do not segment 
form the polar bodies; nor is it probable that there is a general 
