34 H. E. JORDAN 
which will be further discussed below, seems to indicate that the 
sarcosomes are not transient nutritive reservoirs, but are formed 
during the early stages of muscle histogenesis, to remain 
throughout the life of the individual. Apparently only very 
few if any continue to be added, and few if any entirely disappear. 
As the sarcostyles increase in number and grow in girth, probably 
coincident with the growth of the sarcosomes, the sarcostyles 
crowd upon the.sarcosomes and by pressure alter their original 
spheroidal shape into irregular winged forms. 
We come now to the central point of this investigation, the 
presentation of the data which prove that the wing-muscle 
sarcostyle of the wasp passes through the same morphologic 
phases during contraction as the leg-muscle fibrils, that is, it 
undergoes a reversal of striation with the formation of a typical 
contraction band; and, incidentally, that Schaefer’s diagrams 
of muscle contraction are based upon the erroneous interpreta- 
tion of an artifact as a contracted sarcostyle. 
Figure 25 shows the appearance of the wing-muscle sarcostyle 
observed in the fresh condition in Ringer’s solution. The intra- 
sarcostylic telophragmata are very conspicuous as relatively 
coarse stripes, dark at the high level of focus, light at low level. 
The dark dise occupies almost the entire space between successive - 
telophragmata, the light disc appears as a very narrow light area 
on either side of the telophragma. In tissue fixed in Flemming’s 
fluid and stained lightly with iron-hematoxylin the appearance 
of the sarcostyle is practically identical (fig. 26). The light 
dise appears slightly thicker, the fiber as a whole seems to have 
a slightly greater diameter, probably the result of a slight swelling 
action of the Flemming’s fluid; and there occurs a slight con- 
densation of the deeply staining substance in the midregion, 
perhaps indicating the location of the mesophragma. Fixation 
with 95 per cent alcohol causes a shrinkage of the entire sarco- 
style, and a distinct condensation, as the result of dehydration, 
of the deeply staining substance (fig. 27). In such a sarcostyle 
the light disc appears somewhat thicker than the dark disc. The 
dehydrating and shrinkage effect of the alcohol shows mainly 
in Q, demonstrating its relatively more fluid consistency. Fixa- 
