OVARY AND OVARIAN EGG OF ANOPHELES 399 
Most of the material was embedded in paraffin in the ordinary 
way, but this was not very satisfactory, as oocytes containing 
large yolk-masses broke up easily and it was difficult to cut 
uninterrupted series. ‘Towards the end of my work I obtained 
much more satisfactory results using the double-embedding 
collodion and paraffin method described by Newth (21). Using 
this method uninterrupted series of thin sections were easily 
obtained. 
HIBERNATING MosQuiIToEs AND First PERIop oF Kae 
DEVELOPMENT. 
During the winter, female A. maculipennis may be 
found in cowsheds, church towers, and in fact in almost any 
dry and comparatively warm place. They pass the winter 
in a semidormant state, but they are found to feed a little 
during this period, as occasionally an insect with a little blood 
in the abdomen may be observed. A microscopic examination 
of an insect at this stage shows that the fat bodies are 
relatively very large, the ovaries are always very small, in 
the ‘resting stage’, and the spermatheca is full of sperms, 
In cases where the first batch of eggs had already been laid 
and the second was developing, the spermatheca was seen to 
contain sperms, though they were not in such a compact mass 
as in the hibernating insects. As the first males of the season 
had not emerged at this period, it would appear that one 
fertilization of an insect is sufficient for more than one period 
of oviposition. 
The period at which the ovaries of mosquitoes first commence 
to develop depends on the warmth of the season and also on 
the locality. Thus in 1919 the majority of the insects taken at 
the end of March in Kent showed considerable development 
of the ovaries, while a similar degree of development of the 
ovaries was not found till about three weeks later in the 
Shrewsbury district. On March 28, 1920, however, insects 
with the ovaries in the resting stage were only found with 
creat difficulty in the Shrewsbury district. This is no doubt 
due to the early spell of fine weather in that year. 
