452 



Their segmental nature, together with their peculiar mode 

 of development, strongly support the view of Lowne (1890) 

 that they are homologous with the nephridia of annulata. 



Their function is not definitely known; Berlese regarded 

 them as excretory organs. Glaser, in 1912, extracted an 

 oxidising enzyme from them. They appear to be scattered, 

 as a rule, fairly uniformly amongst the cells of the fat-body, 

 and this suggests that they are in some way related function- 

 ally to this structure. Perhaps their secretion contains some 

 enzymes which drive the storage substances of the fat cells 

 into solution, when the organism needs them. 



Their behaviour during development seems to vary with 

 different insects. In Galliphora, Lowne (1890) observed their 

 histolysis during the early pupal period. Perez (1910) 

 observed their phagocytosis and described the oenocytes of 

 the adult fly as arising from certain smaller imaginal 

 oenocytes, present in the body cavity. 



In Galeruca, Poyarkoff (1910) described certain larval 

 oenocytes as undergoing phagocytic destruction at the end of 

 larval life; others bud off numerous daughter cells, which 

 become the oenocytes of the adult insect; the remaining por- 

 tion of such a larval oenocyte becomes, after budding, the 

 victim of the phagocytic activity of the fat cells and 

 leucocytes. 



In the ant Formica rufa, Perez (1902) described a some- 

 what similar budding at the end of larval life. But in CalU- 

 'phora this does not occur. In the honey bee, according to 

 the observations of Nelson (1915), no cell division takes place 

 in the oenocytes, once they have left the ectoderm from which 

 they were formed. Similarly in the chalcid wasp Torymus, 

 Weissenberg (1907) observed phagocytosis of the larval 

 oenocytes at the end of larval life, while the cells of the 

 adult wasp were produced from certain "imaginal oenocytes'* 

 lying within the body cavity. 



When the mature larva of Nasonia is examined the 

 oenocytes are seen as about eight to twelve large cells in 

 each segment from the third to the twelfth, lying on either 

 side of the intestine, and singly distributed, fairly evenly, 

 through the fat-body. They are the oenocytes which have 

 functioned during larval life, and are present already in the 

 newly hatched larva. They are not unlike the cells of the 

 fat-body in appearance at first, but as the latter accumulate 

 storage products the resemblance soon disappears. Towards 

 the end of the first instar the cells have grown a little; they 

 are apparently spherical and measure 12/ji to 13/x in diameter. 



