STRIPED MUSCLE OF WASP 17 
contraction wave are seen to be really due to accumulations of 
sarcoplasm. These accumulations appear as dark lines which 
obscure the continuity of the fibrils, and by contrast cause the 
whole of the sarcomeres between them to appear light”’ (p. 137).27 
The ‘accumulations of sarcoplasm’ that Schaefer here postulates 
are inter-sarcostylic accumulations at the levels of the telo- 
phragmata. But this explanation assumes a beaded condition 
of the sarcostyle with constrictions at the telophragma levels. 
Beading, however, is not a normal accompaniment of contrac- 
tion, but, as will be demonstrated below, a fixation or osmotic 
artifact. Moreover, it must be emphasized that the single 
sarcostyle of wing muscle likewise shows this phenomenon of 
stripe reversal during contraction. In fact, this phenomenon as 
exhibited by a complete fiber is simply the sum effect of the 
stripe reversals in the constituent myofibrils. The explanation 
of the phenomenon on the basis of an accumulation of inter- 
sarcostylic sarcoplasm must, accordingly, for a second reason 
be discarded as inadequate. | 
Still another explanation of this phenomenon of stripe reversal 
as an optical illusion might be based on Schaefer’s diagram?’ 
of the intrasarcomeric changes during contraction (fig. 9). This 
diagram purports to explain contraction as the result of the 
absorption of the ‘hyaline substance’ of the light dise by the 
‘sarcous substance’ of the dark disc. If this be accepted as 
representing actual conditions during contraction, then the 
apparent reversal of striation could very plausibly be explained 
as the result of a relative condensation of the area about the 
telophragma and a relative rarefaction of the area about the 
mesophragma, that is, in the original dark dise. But the direct 
evidence points unmistakably to a movement of fluid in exactly 
the opposite direction from the one here assumed, namely, from 
the mesophragma against the telophragma. We are accordingly 
unable, in view of the microscopic evidence, to escape from the 
conclusion that an actual reversal of striation, as regards the 
dark substance of the sarcoplasm, occurs during contraction. 
Figure 5 shows a reproduction from Schaefer of Englemann’s 
photomicrographs?’ of the same fixed fiber, said to be contracted 
