DEVELOPMENT OF UNFERTILIZED OVA. 47 



covery of the germ-formation of the larvae of some di- 

 pterous insects (Cecidomyia, Miastor). In the ventral 

 cavity of the maggots of these flies arises a second gen- 

 eration of maggots, of which the origin was primarily 

 attributed to a simple germ-formation, until it was 

 shown that these germs proceed from the situation of 

 the sexual glands (which in many insects are deve- 

 loped at a very early stage), and must therefore be 

 regarded as unfertilized ova. The second generation 

 of maggots lives at the expense of its parent, consumes 

 its fatty substance, and afterwards destroys the other 

 organs ; while of the pelican-like parent nothing finally 

 remains but the skin, as a protecting cover to the 

 offspring, which very soon emerges. 



Without mentioning other cases in which it may be 

 questionable whether germs or unfertilized ova attain 

 development, we will point out a few of those in which 

 development, without fecundation, is established with 

 complete certainty. The queen bee, partly from the 

 natural course of its life, partly from various accidenis 

 in which fecundation could not take place, lays regularly 

 a number of unfertilized eggs, from which issue drones, 

 or male individuals ; or if exceptionally eggs are laid 

 by workers, which are imperfectly developed female 

 bees not susceptible of fecundation, these eggs likewise 

 produce drones only. Von Siebold's highly interesting 

 experiments on the reproduction of a wasp (Polistes 

 Gallica), have shown that the hybernating fertilized 

 females, who found a new colony in the spring, deposit 

 eggs whence issue female individuals, and occasionally 

 males. This virgin generation then produces eggs from 

 which males are developed. With various butterflies, 



