158 Proceedings of the Royal Society of Edinburgh. [Sess. 
On entering the periplasm, the cell continues to press on, nucleus foremost, 
until the latter finally reaches the peripheral stratum of the layer, i.e. the 
eosinophil stratum. These cells, which form the blastoderm, divide in future 
in such a way that the long axis of the spindle coincides with that of the 
egg. Up to this stage the mitoses of all the nuclei synchronise, but after 
the formation of the blastoderm this ceases to be the case. 
This building up of the blastoderm does not, as recorded for the eggs 
of some insects, begin sooner at one point than another. On the contrary, 
emigration of the amoeboid cells to the surface occurs at any part. At 
first wide spaces exist between the nuclei which have settled into the peri- 
plasm, but, partly by these nuclei dividing into daughter nuclei lying side 
by side, and partly by the advent of new arrivals, these spaces become 
filled up. Each nucleus exerts an attractive influence on the periplasm 
immediately surrounding it, so that the periplasm becomes broken up to 
form a chain of cell-like “ territories ” each with a nucleus in the centre. 
As each of these is somewhat rounded, the result is to impart to the egg- 
contents a crenated outline by which, even in the living state, this stage 
may be recognised under the microscope. 
Up to this stage a nucleolus has not been demonstrable in any of 
the nuclei of the egg. About the time that the blastoderm exhibits the 
crenated outline just described, every nucleus — both those of the cells 
remaining in the yolk — the vitellophags — and those of the blastoderm — 
exhibits a large nucleolus, and a diminution of the amount of basophil 
chromatin formerly present. Figs. 3a and 36, which show these changes, 
show also that the nuclei of the later stage are smaller than those of the 
earlier one. 
Whether or not the cytoplasm of the amoeboid cells fuses with that 
of the periplasm has been discussed by Marshall and Dernehl in their 
study of the blastoderm of Polistes. They conclude that, after remaining 
for a time distinct, the cytoplasm of the amoeboid cell eventually fuses 
with that of the periplasm. A similar fusion takes place also in Eudemis. 
It is easy to see in my sections stained by eosin and toluidin blue that the 
bulk of the basophil cytoplasm accompanying the nucleus is left behind 
in the basophil stratum of the periplasm, while the nucleus penetrates 
further, the greater part of it lying in the eosinophil peripheral stratum. 
The result is that irregular masses of basophil material are to be seen in 
each cell of the forming blastoderm, projecting into the yolk, though also 
partially in contact with the nucleus. This gives a very irregular outline 
to the young blastoderm on its inner side. Later these irregular masses 
disappear, being incorporated into the cells so that the blue-staining 
