STRIPED MUSCLE OF WASP Dal 
there is absolutely no evidence to indicate that they are only 
open at one end and closed at the end within the dark disc. 
Also, the presence of a bisecting narrow median disc in the dark 
dise shows that the sarcostyle is not actually uncontracted, but 
that it is in an early phase of contraction. 
Sarcostyle B is said to be stretched. This much cannot be 
denied. But we are further led to infer that the occurrence of 
the bisecting median disc is a coincidence of stretching. It may 
be granted that extreme tension may cause a division of the 
dark disc as here illustrated, especially at the very beginning of 
contraction before the initial median dise is clearly discernible. 
But moderate tension effects no such result at this functional 
phase. Tension exerted upon the resting sarcostyle results 
simply in a lengthening of the dark disc. It seems more in 
accord with the histologic data to interpret sarcostyle B as 
one at an early phase of contraction, secondarily modified by 
stretching. 
Sarcostyle C is described as in contraction. It is interpreted 
as demonstrating that no reversal of striation occurs during 
contraction. The deeply staining dark disc, which Schaefer 
identifies with the anisotropic substance, has not moved from its 
original position in the uncontracted sarcostyle on either side 
of the mesophragma. But this sarcostyle is not actually func- 
tioually contracted. It is simply swollen and in consequence 
shortened, that is, artificially contracted, through the endosmotic 
action of the hypotonic formic-acid-water solution. The func- 
tionally contracted sarcostyle has a totally different appearance; 
here a true reversal of striation occurs (figs. 8, 33, and 44). 
Moreover, the unmodified contracted sareostyle is not beaded, 
but maintains a sharp lateral contour. Sarcostyle A is accord- 
ingly an artifact, and cannot properly serve as a basis for the 
construction of diagrams to illustrate the mechanism of muscle 
contraction. If such a sarcostyle is placed in a 2 per cent sodium- 
chlorid solution for several hours, it returns to a condition very 
much like that of sarcostyle C. In other words, sarcostyle A is 
simply sarcostyle C swollen through the action of a hypotonic 
solution. Sarcostyles like that illustrated in C are only found in 
