CELL-DIVISION AND DEVELOPMENT 



result, and concluded that even when the egg approaches the 

 spherical form the symmetry still exists, though obscured. More- 

 over, according to Hallez ('86) and later writers, the egg always lies 

 in the same position in the oviduct, its cephalic end being turned 



a 



, v 



Fig. 129. Eggs of the insect Corixa. [METSCHNIKOFF.] 



A. Early stage before formation of the embryo, from one side. B. The same viewed in the 

 plane of symmetry. C. The embryo in its final position. 



a, anterior end; /, posterior; /. left side, r, right; v, ventral, d, dorsal aspect. (These letters 

 refer to the final position of the embryo, which is nearly diametrically opposite to that in which it 

 first develops) ; m, micropyle ; near/ is the pedicle by which the egg is attached. 



forwards towards the upper end of the oviduct, and hence towards 

 the head-end of the mother. 1 



1 The micropyle usually lies at or near trre anterior end, but may be at the posterior. 

 It is a very important fact that the position of the polar bodies varies, being sometimes at 

 the anterior end, sometimes on the side, cither dorsal or lateral (Ileicler, Blochmann). 



