DEVELOPMENT OF THE OVAKIES IN THE BLOWFLY. 437 
I have, however, been unable to find either the corpuscles 
themselves or the vesicular body they contain imbedded in this 
material ; but bright refractive nuclear particles like the central 
highly refringent body of the corpuscles undoubtedly exist 
in it. 
5. Theoretical Considerations and Conclusions. 
I am led by my observations to the following unexpected 
conclusions : — 
The ovarian eggs in the Blowfly, and probably in other insects, 
are yelks, and contain no germ. 
The so-called gum-glands are in reality germ-glands in which 
the germ-ova are developed. 
These germ-ova pass into the yelks during their passage through 
the oviducts either (a) as naked germinal vesicles, or (b) as female 
pronuclei. 
I shall now examine these hypotheses in relation to tbe work 
of previous investigators, and discuss their probability. 
1. I have already shown that much difficulty exists in attempt- 
ing to reconcile the observations of previous writers on the deve- 
lopment of the ova in insects. So recently as 1881 Prof. Balfour 
(1) regarded the whole question as unsettled, and contented 
himself with stating that the relation of the ovum to the germogen 
and the relation of the yelk-cells to the ovum are points which 
have been especially controverted. I make this observation to 
show that the great number of researches which have been re- 
corded by no means settle the question, which therefore still 
remains an open one. 
2. The existence of true germ-ova, if such they are, in what 
has always been regarded as an accessory gland, although unex- 
pected, is not inconsistent with the probable genetic relations of 
the Insecta. 
llecent embryologicai observations show that the Insecta 
exhibit resemblances, sufficiently startling, to the Nemertid worms, 
and to the Trematodes generally, rather than to the Nematoid 
worms. This is seen by a comparison of the early developmental 
stages of Tineus (Barrois (2)) and Chcetognatha (Kowalevski) with 
those of Musca\ (Kowalevski, Biitschli), my own unpublished obser- 
