Tue Hoc LousE 711 
The follicle epithelium of the egg chamber secretes first the vitelline 
membrane, which in this case is also the cell membrane of the egg, and 
then the chorion. According to Gross, of whose work the following is 
a résumé, the formation of the chorion begins at the posterior end and a 
thin endochorion and a thicker exochorion are formed. The former 
appears striated in section and may be porous. The follicle cells are 
somewhat convex on their inner surface and an imprint of this is left on 
the exochorion. Up to this time their nuclei have been lying toward their 
inner surface, and the formation of the epichorion (exochorion of Leuckart) 
begins as a constriction between the nuclei, and in the indentations so 
formed appear small, rather regularly rhomboid, chitinous structures. 
(The egg shell is not formed of true chitin, since it is soluble in potassium 
hydroxide.) By further constriction of the epithelial cells between the 
nuclei a system of hollow cavities in communication surrounds the egg, 
and these become almost filled by a deposition of chitin forming a distinct 
chitinous lamella (Plate LX VI, 21 and 22). Up to this point a nucleus has 
rested on each side of the constriction, but row the one between the epi- 
and exochorions passes through the canal leaving only a tip of protoplasm 
(Plate LX VI, 23 and 24). The epichorion now moves closer to the eggshell 
proper, and the pores assume the appearance of rather long canals (Plate 
LXVI, 25,a); so that looked at from the surface (Plate LX VI, 26), the 
epichorion appears pierced by numerous canals perpendicular to its surface 
(Leuckart, 1855:140; stomata of Stevenson, 1905:16). Between these 
pores is a network of three-sided cavities. During this development the 
staining properties of the epithelium have undergone a change; the proto- 
plasm takes a deep stain, while the nucleoplasm has become transparent 
and the nucleolus no longer shows great affinity for stain. 
On the operculum there is no epichorion formed and the exochorion 
is much thickened (Plate LX VI, 25,b). The chitin formation extends down 
the sides of the epithelial cells, but it is an outgrowth from the exochorion 
and not a separate formation. There are polygonal areas on the lid 
surrounded by a network whose ridges are much deeper than those on 
the egg, but, as there is no epichorion here, the two parts do not differ 
in level. 
The epithelial cells now rapidly degenerate, and characteristic, very 
darkly stained structures, like broken circles, are seen in their protoplasm. 
On the operculum these are attached to the ridges and extend lengthwise 
