256 WALTER N. HESS 



in no case was there definitely evident a semicircular band-like 

 structure on the intestinal side of the fat-spheres that appeared 

 to be functioning in breaking down these globular masses of 

 cells. It is true that there were a few small leucocytes present 

 at this stage and as the light-organs began to develop, they 

 seemed to increase slightly in numbers. They were not, however, 

 found attached to the fat-spheres as Williams described them. 

 Whether they may function in connection with the early forma- 

 tion of the light-organs was not determined. Because of the 

 apparent increase in numbers, it is possible that they help in 

 breaking down the fat-bodies. 



Since there is a considerable variation in the stage of develop- 

 ment of the Hght-organs in different larvae and pupae, at the 

 same age with respect to the time of pupation, it is diffi.cult 

 exactly to correlate stages in the development of the light- 

 organs with definite periods preceding and following pupation. 

 Among the different series of the developmental stages studied, 

 of the same age, a difference of fully one day is frequently 

 noted in the development of these organs. 



A typical larva, taken about one-half day before pupation, 

 appears sluggish and distended with blood. On sectioning, the 

 light-organ cells usually appear as is shown in figure 12. Certain 

 of the large fat-spheres have ruptured and their cells are being 

 distributed along the hypodermis next to the basement membrane. 

 In certain instances, where the fat-spheres are found lying near 

 and closely appressed against the basement membrane, they 

 are flattened and their cells distributed along the hypodermis, 

 without apparently leaving the fat-spheres. A little later, how- 

 ever, these fat-spheres liberated their cells. A regular gradation 

 in the cells of the fat-spheres in such instances can be seen; 

 those next to the basement membrane are rather flattened, 

 their nuclei larger, their fat globules smaller and fewer in number, 

 and their cell walls more distinct than the cells farther from the 

 hypodermis. As these cells spread out in this manner, the old 

 coverings of the fat spheres disappear, due undoubtedly to the 

 action of the leucocytes. 



