18 
Journal of Agricultural Research 
Vol. XXVIII, No. 1 
logical sections. Giacomini (12) describes those of the larva of Eristalis tenax as 
conspicuous cells, arranged in groups along the sides of the abdomen, near the 
rudiments of the stigmata. 
With the beginning of metamorphosis the fat cells begin to decrease in size. 
When the apple maggot has attained the puparial condition, the oil globules are 
less voluminous and the cytoplasmic strands are proportionately thicker (fig. 6,E). 
Evidently the accumulation of fat reserves has passed its peak and consumption 
has begun. It is to be noted, however, that the granulations in the cytoplasm 
have become more conspicuous and have clearly grown to be small grains suspended 
in the plasma. 
The further history of the fat cells takes us into the period of metamorphosis. 
During the first 48 hours after the formation of the puparium the amount of oil 
in the fat cells continues to diminish, while the granular inclusions of the cyto¬ 
plasm increase in size till they fill the body of the cell from nucleus to periphery, 
though, in general, they are largest and most crowded toward the center (fig. 6, F). 
These inclusions are the albuminoid grains above described. Berlese (4) thought 
that the albuminoid bodies are formed by cell enzymes given off from the nucleus 
acting on materials absorbed from the blood, which is now highly charged with 
the detritus of larval organs. Bishop (8) claims that, in the honeybee, the gran¬ 
ules themselves originate in the nucleus, having “presumably the nature of 
nucleoli”; that, at the beginning of pupation, the nuclear membrane disappears 
and the nuclear granules pass into the cytoplasm where, by “progressive absorp¬ 
tion, both of the surrounding cytoplasmic matrix and of its vacuoles, these 
granules finally develop into globules containing albuminoid material.” Shortly 
after the beginning of metamorphosis in the apple maggot the fat body breaks 
up and its cells float off free in the blood and become spherical (G). At the 
end of the fifth day the cells are mostly 130 to 150 microns in diameter. The 
albuminoid bodies have now reached their maximum development. 
The end of the fifth day after the formation of the puparium marks the time 
allotted to the pupa for attaining its final external form, though the internal pro¬ 
cesses of reorganization go on for several weeks. The fat cells themselves enter 
a period of degeneration. Their shapes become less regular, their proteid grains 
decrease in size and in numbers, while fat globules reappear in the cytoplasm. 
But the globules now bulge at the surface as if the cell wall had become too deli¬ 
cate to retain them (fig. 6, H). By the eighteenth day the fat cells are again 
reduced to masses of oily spheres (fig. 6, I), the droplets swelling out so tensely 
everywhere that the cell walls rupture under the slightest pressure and allow 
the cell contents to be scattered in the blood. Remnants of the albuminoid 
bodies still persist, but they form only a sprinkling of small granules in the 
scanty cytoplasm. 
At last the fat cells break up in the blood by what appears to be a natural 
dissolution of their membranes. Their contents are disseminated, and the blood 
plasma becomes filled with oily droplets and masses of the proteid grains loosely 
held in protoplasmic fragments. At least, the fresh blood of specimens handled 
in the most careful manner is always highly charged with these elements of 
broken fat cells. 
Nearly all investigators have noted this apparent disintegration of the fat 
cells during the later part of the pupal period, but some insist that it is due to the 
preparation or handling of the specimens studied that the fat cells normally 
remain intact and gradually lose their contents by osmosis through their mem¬ 
branes. Some claim also that most of the fat cells finally fall prey to phagocytes, 
and that the remainder persist to regenerate the fat tissue of the imago. Scarcely 
any two writers agree in all details as to the fate of the larval fat cells or the origin 
of the imaginal cells. The reader may find the various interpretations of ob¬ 
served phenomena in the works of Kowalevsky (24), Van Rees (47), Koschey- 
