154 
ME TAMORPHOSIS, 
two, more rounded, and in it is found the micropyle 
(centre of d). One face (^), the future ventral sur- 
face, is convex, the other (e) concave. The shell, or 
chorion, which is very thin, is covered with a delicate 
hexagonal network (Fig. 57, e). The egg consists of 
vitelhis (yolk), in which no nucleus is visible (Fig. 57, 
A, c). Soon at each end of the egg, and at the an- 
terior pole two cells are seen. These are followed by 
four, and so on, all remaining united, and giving rise 
Fig. 57. — Development of Bee. 
to the germinal membrane, called blastoderm^ from 
which the embryo is developed. The cells on the 
dorsal surface soon disappear, and leave the vitellus, 
which consists of oily globules, uncovered over a 
certain area. Then from the cells is formed what is 
called the amnion^ and ventral plate. After that the 
germinal layers appear, during the formation of which 
the edges of the amnion meet over the embryo and 
coalesce. The ventral plates become thickened and 
stratified, the superficial layer {ectoderm) becomes 
separated from the deeper layer {mesoder}n\ and is 
gradually folded on to the dorsal surface, the an- 
terior and posterior portions approach, and ultimately 
