STRIPED MUSCLE OF WASP 47 
portions (spherical in shape) of the myofibrils, horizontally aligned 
close to the telophragma. It appears like a row of granules, very 
similar to the telophragma. It stains like the Q-dise and has 
apparently a similar chemical constitution. Its genetic his- 
tory and its significance, however, remain unknown. It becomes 
involved with the dividing dark dise in the formation of the 
contraction band. 
One of the most interesting and confusing facts regarding the 
accessory disc is its apparently transitory nature. By this I 
mean that it is not always present. It may be present in one 
fiber and absent in an otherwise similar adjacent fiber. Rollet? 
also noted its inconstant nature in arthropod muscle. This in- 
constancy may be genetically related with the formation, or 
degree of development, of the J-sarcosomes, but definite in- 
formation on this point is entirely lacking. 
d. The anisotropic substance 
It was first pointed out by Briicke! (’58) that the intra- 
fibrillar substance of muscle fibers occurs under certain con- 
ditions in alternating strata of isotropic and anisotropic materials. 
Merkel!’ and Rollet” identified this anisotropic substance with 
the material which gives the dark color to the ‘dim’ disc of 
striped muscle when viewed fresh with ordinary light. These 
investigators noted a reversal of striation during contraction 
resulting in the formation of contraction bands. They inferred 
that the contraction band was composed of the anisotropic sub- 
stance of the dim dise of the relaxed fiber. Tourneux®? and 
Rutherford’’ also accept this interpretation of the contraction 
bands. It is significant, however, that none of these investi- 
gators gives an illustration of the contraction bands as seen in 
polarized light under crossed nicols. It has apparently been 
impossible to demonstrate an actual reversal of striae as con- 
cerns the anisotropic materials. Englemann‘! and van Gehuch- 
ten” actually show, as judged from their illustrations, that the 
anisotropic substance does not change its location during con- 
traction. Schaefer?s claims to have demonstrated the same fact 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 27, NO. 1 
