STRIPED MUSCLE OF WASP 37 
(H) dise being conspicuous. The sarcostyle is slightly con- 
stricted at the levels of the dark discs due to the dehydration 
effect of the alcoholic fixation. Beading is clearly a fixation 
artifact, not an index of contraction. This conclusion is further 
supported by the sarcostyle of figure 35. This was an isolated 
sarcostyle lying at the end of a clump, and it was in consequence 
modified to a greater degree. It was, moreover, in the relaxed 
condition. The sarcostyle is sharply beaded, due to an ex- 
cessive dehydration, and consequent condensation, of the dark 
dise. The osmotic effect of a dehydrating fluid, or of a hyper- 
tonic solution, shows itself first, and to greatest degree, in the 
dark disc. This indicates that the dark disc is more fluid than 
the light disc, which latter is in addition held open by the more 
resistant telophragma. If the location of the beads at the 
levels of the telophragmata were here exclusively the result of 
the relatively more resistant nature of the membrane holding 
the fiber open at this point, rather than the result of a relatively 
greater fluidity of the dark disc, the border of the bead would be 
expected to be wrinkled instead of having a sharp contour. It 
might be objected, especially in connection with figure 35, that 
the investigator might readily confuse telophragma and meso- 
phragma, and so misconstrue the osmotic effects of the fixing 
fluids. Determination of telophragma levels, however, is in fact 
a relatively simple matter. The sarcostyles are extensively 
fractured, especially in the sectioned material. The levels of 
fracture in the sections, and in the gold-chlorid and fresh prepa- 
rations, occur almost invariably along the telophragmata. The 
criterion of level of fracture, judiciously applied, in connection 
with the observation of the order of striation in distant parts of 
the sarcostyle, furnishes a precise test for the identification of 
the telophragma in doubtful cases. 
The sarcostyle of figure 36 was fixed with Flemming’s fluid 
and lightly stained with iron-hematoxylin. It appears to be at 
a midphase of contraction. It has special interest because it 
shows the presence of fine constituent sarcostylic ‘metafibrils.’ 
These are especially prominent at the upper end where they 
stained deeply. After Rollet’s method of preservation and 
