164 
J. BRONTE GATENBY. 
position varies little. The row of nuclei which will form 
most of the gut, and which are now sinking in ( N.S.I .) are, 
on the average, a little bigger than the other nuclei. At thb 
anterior pole of the egg, near the letters E.X.N., is seen an 
extruded nucleus. It is a fact that though the main expul- 
sion of nuclei occurs between the stages in PI. 11, fig. 12 and 
fig. 13, even after the throwing out of the central part of the 
egg which contains these large granules, sporadic extrusion 
may take place. That these later extrusions do really occur 
is shown by comparing the size of expelled granules. In 
PL 11, fig. 14, the granule in the anterior end of the egg is 
twice as large as those extruded earlier at the posterior region. 
(Compare also PI. 12, fig. 32.) 
The germ-cells in PI. 11, fig. 14, have changed their posi- 
tion somewhat, becoming arranged towards the ventral edge 
of the posterior pole. In this figure the germ-cells are drawn 
a little darker than they should be. PL 11, fig. 19, is drawn 
from such a transverse section as that through K. in fig. 14. 
The insinking nuclei (N.S.I.) are shown. 
Such an arrangement does not last long, for as the nuclei 
sink inwards they lose their order. This is caused by 
the fact that some lag behind while others penetrate more 
quickly towards the centre of the egg. This is shown in 
PL 11, fig. 15, at N.S.I. By this time these nuclei have 
become very large. The relationship of the various nuclear 
elements in the egg now becomes more complicated, because 
at intervals around the periphery other nuclei grow larger 
and sink inwards (PL 11, fig, 15, at X.Y.). All these nuclei 
are quite distinct from those which were the first to begin 
sinking inwards, and I feel sure that some of them at least 
contribute to the formation of the gut. Others form loose 
cells lying in the cavity between the gut and the ectoderm. 
Often just before and at this stage amitotic division of nuclei 
is found taking place. Moreover, the chromatic arrangement 
of some of the nuclei changes curiously. In these the large 
centrally placed nucleolus becomes ragged at the edges and 
pieces break off and become arranged around the periphery 
