■ Manchester Memoirs, Vol. I. ( 1 906), No. 6. 9 



derived as shown before from the original paranucleus ; 

 and an outer layer of polygonal cells originating from the 

 host. The trophoamnion regulates and controls the food 

 of the embryos which it derives from the blood of the 

 host. In this manner the larvae grow until they attain 

 a certain size, they then enter and live in the blood of the 

 host, and finally, after devouring the vital parts, pupate in 

 the skin of the full grown caterpillar. 



This process of germinogony as observed in Encyrtiis 

 and also in Polygnotus niimitits which Marchal also in- 

 vestigated, has been studied in another Chalcid Litomastix 

 truncatelhts by Silvestri (85). 



Silvestri was fortunate enough to study the maturation 

 of the ovum. He found that the maturation of the 

 parthenogenetic ovum is similar to that of the fertile 

 ovum. Three polar nuclei are formed, which fuse later to 

 form a single nucleus. In the segmentation of the ovum, 

 this single ' polar ' nucleus becomes segmented off in an 

 apical mass of cytoplasm, in which it divides up into a 

 large number of nuclei. As development proceeds, this 

 cap of cytoplasm containing dividing nuclei surrounds the 

 segmenting germ mass; the original ovum is not mono- 

 embryonic, but gives rise to a large number of embryos. 

 These embryos are male if the ovum is parthenogenetic 

 and female if it has been fertilised, as is found in Encyrtus 

 and Polyg7iotus also. 



The fate of the polar bodies is very remarkable in 

 Litomastix, and if the development of this species be 

 compared with that of Encyrtus, it seems probable that the 

 paranucleus of the latter may have arisen from the polar 

 nuclei, though unfortunately Marchal was unable to study 

 the maturation stages. He found the stage with two 

 nuclei, one of which may have been the female pro- 

 nucleus and the other the 'polar' nucleus. 



