DEVELOPMENT OP THE OYARIES IN THE BLOWELT. 



437 



I bave, 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-glauds 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 {h) as female 

 pronuclei. 



I shall now examine these hypotheses in relation to the work 

 of {.revioufe 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. 



Hecent embryological 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 Linens (Barrois (2)) and Chcetognatlia (Kowalevski) with 

 those of iy[«^sc»| (Kowalevski, Btitschli), my own unpublished obser- 



