8 4 



THE EMBRYOLOGY OF THE HONEY BEE 



lies on the dorsal side of the egg with its concave edge directed 

 toward the caudal pole. The caudal fold increases in extent in the 

 same manner as the cephalic fold, progressing slowly toward the 

 caudal pole of the egg, the lines of rupture of the caudal fold 

 and the germ band extending to meet those of the cephalic fold 

 (Fig. 32C). The two folds thus approach one another, the ceph- 

 alic fold moving at a much more rapid rate than its counter^ 

 part ; soon the two meet and fuse near the caudal pole of the egg 

 (Fig. 320 and D). This occurs slightly prior to Stage VIII. While 

 the amnion is thus covering the ventral side of the egg, and 

 consequent to its severance from the edges of the germ band, 

 it also separates from the yolk on the dorsal side of the egg. 

 This separation is directly connected with the separation of the 

 amnion from the edges of the germ band, since it must at the 

 same time also separate from the yolk at this point. The separa- 

 tion thus initiated is continued dorsad, the amnion being, so to 

 speak, peeled off from the yolk, which is thus left bare except 

 for the thin protoplasmic pellicle surrounding it (cf. Figs. 29 and 

 30). When the formation of the amnion is completed, or shortly 

 afterwards, the amnion therefore forms a complete envelope sur- 

 rounding the embryo, and free from the embryo at the two ends 

 of the egg, but closely applied to the embryo elsewhere. Its outline 

 is similar to that of the chorion, except that it is shorter, leaving 

 a considerable space vacant between amnion and chorion at the 

 ends of the egg. Since the space surrounding the egg, between 

 the latter and the chorion, is filled with a watery fluid, it follows 

 that the space between the embryo and amnion is also filled by 

 this same fluid. 



The cephalic fold of the amnion, as described above, is at first 

 composed of cells which are rounded in form (Figs. 246, 26A). 

 As this fold progresses over the surface of the germ band its 

 cells become gradually thinner and flatter (Figs. 26B, 29, 30 and 

 31, Am). At its completion, at Stage VIII, its average thickness 

 is scarcely greater than that of the chorion. At the ends of the 

 egg the amnion is somewhat thicker than elsewhere, and in these 

 regions the nuclei are oval in outline, forming lenticular swellings 

 (Fig. 29). Elsewhere, over the body of the embryo, the amnion 

 is scarcely thicker than the chorion, its nuclei being flattened to 



