DEVELOPMENT OF UNFERTILIZED OVA. 47 
covery of the germ-formation of the larve of a di- 
pterous insect (Cecidomyia, Miastor). In the ventral 
cavity of the maggots of these flies arises a second 
generation 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 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, 
