NEUROPTERA AND COLEOPTERA 



295 



brown. The yolk consists of globules of varying size which are sur- 

 rounded by cytoplasm which, however, is not arranged as a reticulum at 

 this time. The periplasm (Figs. 234, 235) surrounding the yolk in some 

 cases seems to consist of two layers: an outer one which stains more 

 lightly than the inner layer. At the posterior pole of the egg an irregular 





-M 



Fig. 234. — Brachyrhinus. Section through oosome. (pr) Periplasm. 



mass, sometimes saucer shaped, can be seen lying partly in the periplasm 

 and partly in the yolk. This is the oosome, or germinal cytoplasm. The 

 vitelline membrane is difficult to make out, and the chorion is so thin 

 and elastic that it can easily be removed after being pricked with a needle. 

 The location of the pronucleus at the time of oviposition has not been 

 determined with any degree of certainty. In several eggs prior to the 



'X A-'V 



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Fig. 235 — Brachyrhinus Section thiough oobonie (pr) Penplasm. 



formation of the polar bodies it has been observed near one end of the egg 

 (Fig. 236); in others, during meiosis in the periphery about halfway 

 between the ends of the egg. 



A marked thickening occurs in the peripheral cytoplasm surrounding 

 the pronucleus in which the polar body is given off, after which the nucleus 



