682 THE GENERATIVE OKGANS. 
these cells, which are apparently capable of opening and closing 
the micropyle. 
The micropyle is situated in a cup-like depression of the 
chorion, nearly ‘1 mm. in depth, the edges of which arch over 
its cavity and form a kind of hood. The cavity is prolonged as 
a groove to near the posterior egg-pole along the dorsal surface 
of the egg. This is the micropyle canal. 
The Micropyle Canal is about ‘I mm. wide at the anterior 
extremity of the egg, gradually narrowing slightly towards the 
posterior egg-pole. It is formed by two parallel ridges of the 
chorion, which extend backwards from the edges of the hood 
over the micropyle, and is open dorsally throughout its whole 
length (Fig. 97). 
When the chorion is removed from the egg and flattened out, 
a surface view of the micropyle canal can be obtained. It is 
then seen to exhibit a granular appearance, which renders it 
darker and less transparent than the rest of the chorion. The 
granules appear to lie in the substance of the chorion between 
the outer and inner layers. 
The significance of the micropyle canal is unknown. 
Henking [850] states that he found spermatozoa in the canal 
in eggs which had just been deposited ; and it appears indubit- 
able that it is in some way concerned in the fertilisation of the 
egg. Herold thought that it is concerned in supplying the 
larva with air during its development, as both the micropyle 
canal and the cavity at its anterior extremity in which the 
micropyle is situated are filled with air in the eggs a short time 
after they are laid. There is no reason, I think, to ascribe a 
respiratory function to it, as the anterior extremity of the egg 
is exposed to the air, and the micropyle canal falls short of the 
posterior egg-pole and ends by becoming more and more 
shallow, so that it could hardly be efficient in conducting air 
from the anterior to the posterior egg-pole. 
I think there is some reason to believe that the original 
position of the micropyle in the earliest forms of insects may 
have been at the posterior egg-pole, and that the micropyle 
canal represents a long micropyle apparatus produced by the 
