312 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



Leiby and Hill (1923) state that this species develops both monembry- 

 onically and polyembryonically. Both fertilized and unfertilized eggs 



will develop, the fertihzed eggs pre- 

 sumably giving rise to females. The 

 egg is somewhat larger than a single 

 blastoderm cell of the host egg (Fig. 

 259). If the egg is inseminated, the 

 sperm can be seen in a curved or 

 arched position (Fig. 260A). Never 

 more than one sperm is found in one 

 egg. The so-called "germ-cell deter- 

 minant" (oosome) is apparently 

 lacking. The nucleus is regularly 

 found near the center of the newly 

 deposited egg. Later it increases in 

 size and gives off two polar bodies. 

 After the second division the second 

 polar body is seen at the anterior 

 end, near the first polar body. The 

 oocyte nucleus (later the female pronucleus) after the ninth hour may be 

 found in the posterior half of the egg, increasing in size. After the second 

 maturation the male pronucleus becomes spherical and about the six- 



nu.p 



Fig. 259. — Platygaster. Egg of para- 

 site (e) under the blastoderm {bid) of the 

 host egg. 



A B C . 



Fig. 260.— Platygaster. A, egg one hour after deposition. B, male and female pronuclei 



about to fuse. C, egg one to two days old. (nu) Nucleus, (nw. /) Fusion nucleus. 

 p) Paranuclear mass. {nu. pr) Pronuclei, (sp) Sperm. 



{nu. 



teenth hour fuses with the female pronucleus (Fig. 2605). The fusion 

 nucleus is now in the posterior region of the egg, whereas the polar nucleus 

 {nu.p) made by the fusion of the two polar bodies lies in the anterior 



