453 



The cytoplasm is fairly clear, tliougli with a very faint indica- 

 tion of granulation; the outermost regions are faintly vacuo- 

 lated. The nucleus is large, measuring 5J/x to 6fx in diameter; 

 its chromatic contents are fairly evenly scattered and there 

 is one large central karyosome. 



During larval life the oenocytes grow considerably in 

 size, having in the mature larva a diameter of about 45/x 

 (sometimes as much as 55/x). The nucleus grows in propor- 

 tion; its diameter is about 25/x. There is no evidence, there- 

 fore, of any marked difference in the nucleo-cytoplasmic ratio 

 in the young and old larvae, so far, at any rate, as the actual 

 volumes of the two materials are concerned. Whether there 

 has been an increase in the quantity of chromatic material is 

 more difficult to observe; there seems, however, to be no 

 evidence that such has occurred; the great karyosome has 

 disappeared and scattered its contents throughout the 

 enlarged nuclear space; in its place, however, are to be seen 

 one or a few prominent nucleoli often containing crystals; 

 sometimes as many as twenty smaller ones are present 

 instead. The cytoplasm is generally faintly granular, and 

 usually heavily vacuolated in its outer regions (fig. 76). 

 Generally the oenocytes are spherical, but often they become 

 partly indented by other organs — tracheae or muscles — against 

 which they have been pressed as they gradually grew in size. 



In the late larva and in the earliest hours of the pupa 

 these cells degenerate and finally disappear, and all stages of 

 degeneration may be observed during this period. Often in 

 the mature larva the oenocytes may show a division of the 

 cytoplasm into an inner heavily granular and an outer less 

 granular zone, which is to be looked upon, apparently, as the 

 beginning of disorganization. But it is not tijl the time of 

 pupation that actual disintegration occurs, " 



Usually the surrounding fat cells prevent the approach 

 of leucocytes, and the oenocytes disintegrate spontaneously; 

 large rents appear in the cytoplasm, and these develop into 

 great holes; and at other times the' whole cytoplasm 

 degenerates into a fine powder, which is cast into the blood 

 (figs. 176, 177). 



But when the surrounding fat cells are not so densely 

 packed as to prevent the leucocytes from taking part in the 

 process, the latter appear (fig. 178), and, before chemical 

 disintegration has had time to occur, they overwhelm the 

 cells and, eating large pieces out of their substance, eventu- 

 ally devour them. So far as I could observe, the larval 

 oenocytes do not persist beyond the early hours of the pupal 

 stage. 



Meanwhile, the oenocytes of the adult wasp have been 

 developing. They are represented, in the defaecating larva, 



