682 THE GENERATIVE ORGAXS. 



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 'I 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 [350] 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 



