STRIPED MUSCLE OF WASP 45 
which the sarcosomes have been dissolved by alcoholic fixation 
(figs. 14 and 19). Both accessory dise and contraction dise are 
primarily and essentially intrasarcostylic (fibrillar) elements. 
The sarcosomes of the wing muscle of the wasp differ markedly 
in certain respects from those of the leg muscle. In the first 
place, there are no really smaller sarcosomes, such as correspond 
to the J-granules of the leg muscle. This would seem to indi- 
cate that a new formation of sarcosomes does not occur, or only 
occurs to a slight degree, perhaps only in certain young fibers. 
In the second place, the sarcosomes are not grouped at definite 
horizontal levels, but lie between adjacent sarcostyles in short 
oval groups (fig. 21) or long columns in single or double file 
(hig 23),. 
The wing-muscle sarcosome is a primarily oval body, which 
becomes secondarily modified, through the operation of mechan- 
ical factors incident to the mutual pressure of adjacent sarco- 
styles, Into very irregular forms. Transverse sections of these 
fibers show that the modified sarcosomes have long, lateral, 
wing-like processes (the result of pressure) which connect with 
similar processes from adjacent sarcosomes to form in some 
instances a complete sheath for the involved sarcostyles. Frag- 
mented or unusually pale sarcosomes were not seen in this 
tissue. This suggests that the life of the sareosomes is not here 
a transient one, but that once formed the sarcosomes persist 
probably throughout the life of the muscle fiber. Alcoholic 
fixation causes collapse of certain large sarcosomes, indicating the 
extraction of fluid by the alcohol. But the sarcosomes are in 
general almost as well preserved in alcohol, except for occasional 
wrinkling of contour, as in Flemming’s fluid or 10 per cent 
formalin. 
These reactions to fixing fluids indicate that the wing-muscle 
sarcosomes consist of some substance in addition to lipoids. The 
complete genetic history, chemical condition, and functional sig- 
nificance of the sarcosomes remain for the present unknown. 
We are probably quite safe, however, in assuming that the 
sarcosomes here described for the leg and the wing muscle of 
wasp are essentially the same thing, representing simply less 
