61 

then do they acquire a nucleus? Two hypotheses have been consid- 
ered, one of which has a considerable body of evidence in its support. 
In the first place, the nucleus might arise from chromatin granules 
which break away from the chromosomes during the formation or 
condensation of the spindle. There is, however, no evidence for this 
view, since the entire chromatin content of the odcyte nucleus seems 
to take part in the formation of the spindle and later the keimbahn- 
chromatin. ‘The second hypothesis was suggested when a number of 
cases were discovered of two oöcytes lying end to end without any 
intervening follicular epithelium. This hypothesis is that pairs of 
oöeytes unite end to end, the posterior oöcyte containing the keim- 
bahn-chromatin and the anterior furnishing the egg nucleus. Stages 
in this process are shown in Figs. 15, 16, 17 and 18. 
As the oöcytes increase in size and age the follicular epithelium 
becomes gradually thinner and in several instances only a delicate 
strand could be observed between the ends of adjoining oöcytes. In 
Fig. 15 two oöcytes are shown without any cellular layer between 
them although the follicular epithelium extends in a short distance 
at the point of contact (w). The posterior cell is much the larger 
and older, and possesses keimbahn-chromatin, but no nucleus. The 
other oöcyte is younger and smaller and contains what has been 
interpreted as a disintegrating spindle (s). The condition illustrated 
in Fig. 16 is similar except the keimbahn-chromatin in the posterior 
oöcyte is less regular having already begun to break up, and the 
chromatin rods in the anterior cell represent a further stage in the 
transformation of a spindle into a nucleus. Fig. 17 illustrates what 
is considered a later stage in the fusion process. The anterior part, 
which contains a definite nucleus, is connected with the posterior 
portion by a thick strand. The nuclear membrane is not very distinct 
in the preparation indicating that the nucleus is not yet completely 
formed. The posterior part is not as large as in the other figures since 
the section was not exactly in the longitudinal axis but slightly oblique. 
The keimbahn-chromatin has been added in the figure from a part 
of the odcyte three sections away. A still further stage of fusion is 
indicated in Fig. 18. 
In all these cases and in fully developed eggs (Fig. 1) there is 
a distinct waist line which can be accounted for upon the view that 
two odcytes fuse end to end as above described, the narrow part 
corresponding to the region of union. The conclusion seems warranted, 
