MATURATION OF UNFERTILISED EGG IN TENTHREDINIDA. 561 
On the Maturation of the Unfertilised Egg, and 
the Fate of the Polar Bodies, in the 
Tenthredinideze (Sawrflies). 
By 
L. Doncaster, M.A., 
Mackinnon Student of the Royal Society. 
With Plates 35 and 36. 
1. InTRODUCTION. 
Tue work described in this paper was undertaken to 
determine, if possible, what is the function of the polar 
bodies, and whether they are connected with the origin of 
the germ-cells, in a parthenogenetic insect. It has been 
maintained by Petrunkewitsch (9, 10) that in the unfertilised 
egg of the honey bee, which gives rise to a drone, the second 
polar body unites with one half of the first, and that the 
“copulation-nucleus ” so formed gives rise to the testes of the 
bee. Castle (1) has further taken the facts given in the 
papers of Petrunkewitsch and used them in formulating a 
suggestive hypothesis as to the heredity and determination of 
sex on Mendelian principles. It seemed, therefore, desirable 
that the matter should be investigated in other cases, and the 
sawflies were chosen as a likely group in which to work at 
the problem. 
The sawflies are in many ways admirably suited to such 
work; many species are common and easy to rear; the eggs 
frequently develop when unfertilised, and in some species 
males, in others females, and in a third group both males and 
females are produced from parthenogenetic eggs. The eggs 
also are readily laid in captivity, and can be preserved at 
