380 ARTHUR DENDY. 



Stage B. — This stage was found in an animal which had 

 lain for a long time in spirit previous to dissection, and the 

 chorion had assumed a brown colour. Where thin places 

 occurred in the Queensland specimen we now find thick ones, 

 forming rounded protuberances very regularly scattered over 

 the surface (figs. 20, 21, 22). The chorion now consists of 

 two distinct layers, an inner much thicker one exhibiting 

 radial striation and evidently corresponding to the chorion 

 as already described in Stage A, and an outer one which is 

 a new formation — or at any rate was only beginning to be 

 formed in the preceding stage. This outer layer is developed 

 chiefly, it' not entirely, over the thin clear areas in the inner 

 layer, which thus come to protrude externally in the form of 

 low, rounded knobs. The outer layer is for the most part 

 clear and structureless, and has a chitiuoid appearance, but 

 in this particular specimen a group of highly refringent 

 granules is very conspicuous in the middle of each protuber- 

 ance. This clear outer layer of the chorion probably increases 

 in thickness as the egg passes down the oviduct.-^ 



Stage C. — This stage occurs in eggs which have been 

 deposited, and may be regarded as the mature condition. 

 The two layers are still clearly recognisable (figs. 25, 26). 

 The inner one exhibits the usual radial striation, but it no 

 longer shows the thin areas of the first stage, which seems to 

 indicate that unequal thickening has taken place in it. The 

 outer layer is clear and transparent, and the refringent 

 granules of the preceding stage are no longer visible. 

 The extent to which it has become thickened varies in 

 different cases ; fig. 26 shows, in optical section, a specimen 

 in which the protuberances remain comparatively low, though 

 the outer layer is clearly recognisable even between them. 

 Fig. 25, on the other hand, is drawn from a specimen in 

 which the protuberances were remarkably strongly developed. 

 After the deposition of the egg, the outer layer of the chorion 



' It seems possible tliat tiie nucleus. like bodies observed in Stage A may 

 belong to cells wliicli are concerned in the formation of tlie outer layer of the 

 chorion. 



