154 J. BRONTE GATENBY. 
Ill some cases the eggs were pricked and the whole thrown 
into picro-nitric. 
After some trials Petrunchekewitsch was almost exclusively 
used, and in most cases it gave a fine fixation, but not always. 
In using this fixative it is not necessary to prick the eggs. 
Ordinary preservatives like Bouin, corrosive acetic, or 
Flemming will not penetrate the chorion. This at once 
causes difficulties, for alcoholic fixatives are not always 
reliable. The eggs were left over night in the Petrunche- 
kewitsch and washed out in 70 per cent, alcohol. 
When in xylol the eggs were pricked with a fine needle 
and placed in the paraffin bath. It was not always possible 
to successfully prick the eggs, but unless this was done it 
was necessary to leave the masses longer in the bath. This 
hardens the eggs and makes sectioning a dreadfully difficult 
task. The eggs were cut in their groups, 5 jjl in thickness, 
on a Yung microtome, each section being painted with 
celloidin and ether. One could not be sure that the eggs 
were not parasitised until after staining, and three or four 
batches would often be cut without finding any stages. It 
was only by staining overnight in Iron Haematoxylin that a 
a suitable differentiation could be got. Ehrlich and the 
carmines were useless. In some cases alternate slides were 
counterstained in orange G. or dilute acid fuchsin. 
General Facts Concerning the Appearance of the 
Material in Sections and in Whole Mounts. 
In PL 11, fig. 8, there is drawn a part of the section of a 
parasitised egg-mass. The larval parasite (D.P.) lies in the 
yolk of the Donacia egg, and a little to the right and lower 
edge of the larva is the remains of the embryonic gut of the 
host {Gr.). At N.S. are the remains of the Donacia larva’s 
nervous system, and below at I is a still recognisable de- 
generate leg. The parasite has reached the stage just before 
it begins to swallow the yolk in which it lies. Abutting 
against the chorion of the egg in the middle of the field are 
