1911.] Gametogenesis of the Gall-Fly, N. lenticularis. 481 
reduced number of chromosomes. The whole process is so nearly simul- 
taneous as to give the impression of a single division, a fact which led me to 
hazard the suggestion in Part I of this paper that only one maturation 
occurred in the parthenogenetic eggs. The fresh material since collected, 
however, shows that the inner chromosome group does undoubtedly divide 
just after its separation from the outer, and the phenomena must therefore 
be interpreted, as in the summer eggs, as a modified double polar division. 
The maturation thus differs rather in detail than in essence from what occurs 
in all other Hymenoptera in which the polar divisions have been examined. 
After the polar divisions, the egg-nucleus sinks into the yolk and almost 
immediately forms the first segmentation spindle, so that the prophase of this 
mitosis may not rarely be found in the same section with the polar chromo- 
somes. The axis of the first segmentation spindle appears usually to he 
nearly, but not quite, parallel to the long axis of the ege; after the division 
is completed, the daughter nuclei travel widely apart, so that the division- 
figures of the second segmentation mitoses are usually widely separated. In 
these and the later segmentation divisions the chromosomes are most easily 
counted in anaphase ; in metaphase they may be clumped, but, even so, differ 
from the clumped diploid groups described above in their smaller size. In 
anaphase figures cut across it is possible to count 10 with confidence in some 
cases (fig. 15), and in a number of others to see clearly that the number is 
undoubtedly much less than 20, though not accurately countable (figs. 16, 
a,b; 17,a,6). In a few cases one chromosome appears to lag very much 
behind the others, as if it was being left out of the nucleus altogether, but 
in other eggs I have not seen anything of the kind, even when mitoses of 
the same stage are present. During the segmentation mitoses, the groups 
of polar chromosomes persist at the edge of the egg (fig. 18), but when 
the nuclei come to the surface to form the blastoderm, they are no longer 
recognisable. The chromosomes and mitotic figures in the blastoderm 
divisions are too small and crowded for counting to be possible. 
Later Stages: Segmentation and Blastoderm. 
I have no great number of sections of eggs in the later segmentation and 
blastoderm stages, but among them are some which show phenomena of 
interest. In eggs which have a well-developed blastoderm, a number of 
nuclei remain in the yolk, and these are often of two types in the same egg. 
There are a number of rather large vesicular nuclei, sometimes showing a 
faint reticulum, and, in the others, a clear space inside the membrane 
enclosing a more compact stained mass, rather suggesting that the nuclear 
contents have contracted. Among these there are frequently many smaller 
