THE MICROPYLE 



523 



dear, oval spots, the long axis of which is parallel to the long 

 axis of the egg. 



"With a higher power the tube of each funnel is clearly visible as a thin 

 canal which dilates rapidly into the large oval aperture on the outer face of the 

 chorion. The narrow tube is sometimes fully as long as the large oritice. The 



Z-. 



gs 



FIG. 499. a, fragment of a micropylar papilla, showing 

 its lumen ; b. optical section of another papilla, in this one the 

 lumen extends to the vitelline membrane, but does not pass 

 beyond it; c, d, e, and/, papilla- of different forms. A, an- 

 terior end of an ovarian egg, showing mode of growth of the 

 inicropylar papillae : <t. fi, two successive stages ; c, surface 

 view of modified papilla; from the lower edges of the cap ; d, 

 tunica propria of the ovariole ; <?, remnant of the cell-mass that 

 secreted (.'?) the inicropylar cap. After Ayers. 



FIG. 500. Egg of Pfrla 

 maxima: c, chorion; d, ofilem- 

 ma : ys, glass-like covering of 

 micropyle ; I, cavity under 

 same ; g, canals penetrating 

 chorion. After Imhof, from 

 Sharp. 



micropylar perforations are all directed from the germarium to the vaginal pole 

 of the egg. Hence a line, the hypothetical path of the spermatozoon, drawn 

 through one of these oblique micropyles, and continued into the egg, would 

 strike the equatorial plane. The female pronucleus, as we shall see further on, 

 moves in this plane." (Wheeler, p. 289.) 



The micropylar region is generally, at least in Orthoptera and 

 Odonata, covered by a gelatinous cap (Figs. 499 and 500, gs), which 

 may form a covering membrane 

 which extends over a large part 

 of the egg, or may envelop the 

 entire outer surface. In some 

 cases micropyles are scattered 

 over the entire surface of the 

 egg, but usually the perforation 

 is situated at the end, and is 

 often guarded by raised pro- 

 cesses, either one or several, like 



. FIG. 601. Micropyles : <7, of Nepa cinerea ; 



bristles, or toadstools, etc., these b, of Loeusta viridissima ; c,_ofabug(PyrrAo- 

 . . ln , ... cor is apterus). From Gerstacker. 



being especially characteristic of 



the eggs of certain Hemiptera (ISTepa, Fig. 501, a, and 'Eanatra), or 

 the region is variously sculptured, as in the eggs of butterflies. In 

 the micropylar apparatus of (Eeanthus the papillae have a distinct 

 lumen (Fig. 499), or a channel for the ingress of the male filament. 



