578 



distinct ducts, so that probably each egg-germ has a separate yolk 

 duct. 



In Nepa there is a large lateral projection at the anterior end of 

 each egg, and it is always on the same side as the germinal vesicle ; 

 but this latter varies from side to side without any apparent 

 regularity . 



In the common earwig, the egg-tubes are short and numerous ; 

 each consists of a large, lower chamber, which is more or less pear- 

 shaped, and two or three other chambers, but slightly separated from 

 one another, bent down on the lower chamber, and so short and 

 small as to resemble very closely the stalk to the pear. 



Each egg-germ in this insect consists of two parts ; an egg-cell 

 containing the germinal vesicle and the yolk, and a vitelligenous 

 cell. The vitelligenous cell has no distinct nucleus, and in the 

 small stalk-like part of the egg-tube is double the size of the egg-cell, 

 which at this period contains the germinal vesicle, but not as yet 

 any yolk matter. In this part of the egg-tube it sometimes appeared 

 as if there were two vitelligenous cells to one egg-cell. In the large 

 lower egg-germ this is never the case. In this part of the egg-tube 

 the vitelligenous cell is still larger than the egg-cell, which however 

 grows larger, both absolutely and relatively, until it almost fills the 

 egg-chamber. 



The yolk mass in the lower egg-germ consists of dark granules 

 and oil globules surrounding the germinal vesicle, which generally 

 contains two or three minute cell-like vesicles. The contents of 

 the vitelligenous cell are light brown, granular, and in part arranged 

 in somewhat cylindrical masses, which lie generally rather trans- 

 versely to the egg-tube, and do not appear to have any firm 

 boundaries. At least, I was never able to isolate them, except after 

 applying reagents, as, for instance, acetic acid, and then only some- 

 times, and with difficulty. They then appeared to be somewhat 

 elliptic in shape. 



From M. Leon Dufour's description, the ovary in Labidura gi- 

 yantea is entirely unlike that of Forficula. 



The egg-formation in Forficula is not the least remarkable 

 peculiarity of this extraordinary genus, and does not at all resemble 

 that of either the Coleoptera or the Orthoptera. 



The Neuroptera (except the Libellulina) offer the next step to- 



