56 CHARLES PACKARD. 



After the sperm enters, the first maturation is completed 

 normally and the chromosomes become arranged on the second 

 polar spindle. There are very few exceptions to this, even in eggs 

 exposed for a long time. Fig. 2 shows a condition which may be 

 found occasionally in eggs treated for 80 minutes or more. It is 

 evident that the whole egg, both chromatin and protoplasm, has 

 been greatly disturbed, for the sperm after entrance has failed to 

 develop normally. In the course of normal development it 

 grows into a large vesicle by the time it has reached the vicinity 

 of the egg nucleus, but in this case there is no evidence of any such 

 growth. The tripolar spindle of the first maturation division 

 indicates again how extensive is the injury to the egg. The 

 extra aster may be derived from the sperm aster, or possibly both 

 sperm asters are involved, one having fused with the egg aster; 

 or the latter may have divided, while the sperm aster has not 

 developed at all. The latter view is very likely correct for in 

 other eggs similarly treated the sperm may be seen lying in the 

 center of the egg without any trace of centrosome or asters. 

 Whatever may be the right interpretation it is evident that the 

 egg protoplasm has been injured to such an extent that the sperm 

 cannot develop normally. The same phenomenon can be seen 

 in the eggs of Nereis similarly treated. The chromosomes on 

 the tripolar spindle show no signs of fragmentation but they 

 have not divided, and some of them are irregular in shape. But 

 in eggs treated up to 45 minutes the formation of the polar bodies 

 and the development of the sperm is practically normal. The 

 egg nucleus in a fairly large proportion of cases develops nor- 

 mally after the extrusion of the polar bodies and fuses with the 

 sperm nucleus. The subsequent development of such eggs will 

 be described later. 



In a considerable number of eggs exposed for periods up to 45 

 minutes the egg nucleus does not behave noimally. Instead of 

 moving inward to meet the advancing sperm, it tends to remain 

 in its original position under the polar bodies, there developing 

 into the vesicular stage. Fig. 3 illustrates this condition. Here, 

 although a part of the nucleus has moved inward, there still re- 

 mains a part of it directly under the polar bodies, connected with 

 the rest by a protoplasmic bridge. The distribution of the chro- 



