XXX Introduction. 



plasm from the fertilized polar bodies of the sexual 

 generation, produces from i,ooo to 1,200 eggs ; or in an 

 approximate proportion to the number of chromosomes 

 postulated as present. 



The impression which long prevailed that one sperma- 

 tozoon was equal potentially to one ovum, led observers 

 to regard the presence of more than one spermato- 

 zoon as an act of 'polyspermy,' as abhorrent to nature, 

 and a cause of monstrosity \ But Kupfifer, Benecke 

 and others record the fact that spermatozoa do enter the 

 'peculiar protoplasmic protuberances,' many appearing to 

 form pronuclei after gaining access to the ovum, so that 

 in numerous species polyspermy appears to be the rule. 



A great deal has recently been done in working out 

 the development of the reproductive rudiment in insects, 

 and it seems that the cells which become the ova, and 

 which I believe to be chiefly those primarily set 

 aside in the polar bodies with or without corresponding 

 spermatozoa, can be traced to the rudiment of the germ 

 and sperm-tracks of the embryo. These germinal track- 

 cells, formed by the first segmentation, surround the 

 primitive germ-cells to form with them the rudimentary 

 reproductive organs. In the germogen one germ-cell 

 and a nutritive circle of germinal epithelium cells form 

 a cluster, and these grow forward together, the ger- 

 minal epithelium growing in between each batch. In 

 the upper part of the developing egg-tube, each batch 

 is very small, but as it advances it increases steadily 

 in size. In the egg-tube of the Cynipidae the egg-stalk 

 curves round the next t^^, and the clubbed end of the 

 stalk gives the appearance of a large and small egg 

 alternating. 



In some asexual species of Hemiptera the oocyte, 



^ Selenka, Y.., Befruchtung des Eies, 187 1. 



