440 FRANK R. LILLIE 
the egg and sperm nuclei. Some such cases were found, but they 
were much fewer in number than expected on the basis of the 
number of partial sperm nuclei found in earlier stages. I was 
therefore led to suspect that the smallest sperm nuclei might dis- 
integrate prior to this time. However, I have failed to find 
direct evidence for this. It may be, therefore, that the failure 
to find the expected number of partial sperm nuclei in the stage in 
question is due to the fact that the critical period for such deter- 
mination is of very brief duration. 
Fig. 42 illustrates a case of disparity between the two germ 
nuclei. Five sections are involved, and the male and female 
nuclei are indicated by the appropriate signs. The male com- 
ponent, distinguished by its accompanying aster, exhibits five 
nucleoli and the female thirteen. The volume of the female 
component is also much greater than that of the male compo- 
nent. I believe, therefore, that we have here an undeniable case 
of fusion of a partial sperm nucleus with an entire egg nucleus. 
In the stage of the first cleavage spindle of eggs centrifuged 
just before penetration of the spermatozo6n we have three classes 
of eggs, aside from a very few polyspermic eggs: (1) Some with a 
more or less normal cleavage spindle; (2) some with a monaster 
centered in a group of chromosomes; (8) some without any trace 
of astral radiations although chromosomes are formed. In a 
particular lot of eggs (7.4 of 1911) of which 10 per cent segmented, 
at the stage of the first cleavage the first class is rare, the second 
class is quite common, and the third is the most frequent condi- 
tion. The first class evidently eae ponds to the 10 per cent of 
eggs that segmented. 
The two latter classes are illustrated in figs. 48 and 44. Fig. 
43 is a camera drawing of the three sections of the nucleus of a 
single egg belonging to the third class. The eggs of the first class 
of the same lot were in various stages of the anaphase and telo- 
phase of the first cleavage. There appear to be fourteen chro- 
mosomes, the number usually found in the maturation spindles; 
the position near the animal pole proves it to be the egg nucleus. 
The absence of the sperm nucleus is readily demonstrated. There 
is an entire absence of all radiations in the cytoplasm. Both 
