162 
J. BRONTE GATENBY. 
widespread, and by the stage in PI. 11, fig. 14, no granules 
are left and all nucleolar masses are found in the mid-region 
of the nucleoplasmic mass. I have not discovered the early 
blastoderm form of nucleus in any other stages. 
PI. 11, fig. 18, is a transverse section of an interesting- 
stage. It shows that the blastoderm nuclei have grown and 
that changes have taken place in their disposition, while the 
mass of extruded nuclei which, in PL 11, figs. 12, 13, 16, and 
17, was situated in the centre of the egg, appears to be 
shifting outwards. Now, an examination of all later stages 
after the blastoderm will reveal the fact that the extruded 
nuclei leave their central position in the egg, and pass to the 
periphery (see PI. 11, figs. 14, 15, 18, 19, 24, 25, and 27, 
E. X.N.). 
It is just after the stage drawn in PI. 11, fig. 12, that this 
occurrence takes place, and PI. 11, fig. 18, shows what 
happens. The central mass containing the nuclei, as is seen 
in PI. 11, fig. 13, is somewhat vacuolated. Almost the whole 
of this central region streams out to the periphery, carrying 
the extruded nuclei with it, and breaking through and 
disarranging the layer of blastoderm nuclei on one side; in 
the process several healthy nuclei are carried out as well 
(PI. 11, figs. 18 and 19, L. E. N.). The space left by the out- 
streaming mass is soon closed up, and the disarranged nuclei 
resume their places ; the new membrane appears between the 
re-formed blastoderm and the extruded mass (M. B., in PL 11, 
fig. 19). 
Regarding the position in which this final expulsion of 
extruded nuclei takes place, though no absolute regularity 
exists, it is a fact that the outbreak appears generally towards 
the middle at any place, but more often than not on the future 
dorsal side of the embryo. In PL 11, figs. 14, 18, and 19, it 
was ventral; in PL 11, figs. 15 and 25, it was dorsal. In 
PL 11, fig. 14, it wiis near the posterior pole; in the others 
about median. 
As will be seen in PL 11, figs. 15, 18, 19, and 27, at 
E. X. N. this extruded mass is quite large and consists of the 
