38 H. E. JORDAN 
staining, a similar phenomenon occurs. Figure 46 illustrates an 
end view (optical transverse section) of a sarcomere from such 
a preparation. Here the constituent metafibrils are largely 
grouped in the manner of more or less sharply contoured circles. 
The latter suggested to Schaefer the idea of a poriferous con- 
dition of the dark disc. These ‘pores’ certainly are fixation arti- 
facts. Whether the fibrils (metafibrils) should be similarly 
interpreted, or whether this technic simply rendered more con- 
spicuous constituent metafibrils of the sarcostyle, cannot be 
finally decided. These sarcostyles, certainly under most con- 
ditions, both fresh and fixed, both in longitudinal and transverse 
section, appear homogeneous (figs. 23 and 48). This homo- 
geneity may be simply due, however, to a closely similar refrac- 
tive index on the part of these metafibrils and the intrasar- 
costylic sarcoplasm, so that the presence of the metafibrils cannot 
be discerned until rendered conspicuous by certain fixing and 
staining processes. 
Figures 37 to 44 are twice the magnification of figures 25 
to 36, namely, 2600 diameters. They are all of sarcostyles of 
the wing muscle of the wasp, from tissue fixed with 95 per cent 
aleohol and stained with iron-hematoxylin. Figures 37 and 38 
are both of relaxed fibers, as indicated by the undivided condition 
of the dark disc. The question arises as to why the dark disc 
of figure 37 is more than twice the length of that of figure 38. 
It will be noted also the dark disc of figure 38 is more compact 
than that of figure 37, which latter is, moreover, slightly lighter 
in color and apparently longitudinally striped. The short length 
of the dark dise of figure 38, as compared with this dise of the 
relaxed fiber in fresh condition or after Flemming’s fixation 
(compare with figs. 25 and 26), is the result of the dehydrating 
(condensation) effect of the alcoholic fixation. The greater length 
and somewhat different character of the dark disc in figure 37 is 
to be explained in terms of a secondary stretching of the fiber. 
These two sarcostyles illustrate the primary effects of exosmosis 
and mechanical tension upon the dark disc, results to be expected 
if the dark disc is relatively more fluid than the light disc. 
