FIG. 508. Fertilization of the egg of a round-worm (Aacarin megalocephala) : A, the ends 

 (centrosomes) of the spindle formed. , the spindle completed ; xp, sperm-nucleus, with its 

 chromosomes ; ei, egg-nucleus ; p, polar bodies. After Boveri, from Field's Hertwig. 



FIG. 493. Eggs of Corixa : A, early stage before formation of the embryo, from one side. B, the 

 same viewed in the plane of symmetry. <?, the embryo in its final position ; a, anterior, p, posterior, 

 end ; I, left, r, right, v, ventral, d, dorsal, aspect. (The letters refer to the final position of the 

 embryo, which is nearly diametrically opposite to that in which it first develops) ; m, micropyle ; 

 p, pedicle. After Metschnikoff, from Wilson. 



