DEVELOPMENT OF UNFERTILIZED OVA. 47 



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

 terous 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 sex- 

 ual glands (which in many insects are developed at a 

 very early stage), and must therefore be regarded as un- 

 fertilized 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 accidents 

 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. 



