STRIPED MUSCLE OF WASP 29 
Figure 14 should be considered in connection with figure 18. 
The latter was fixed with Flemming’s fluid and lightly stained 
with iron-hematoxylin. The myofibrils are discernible, but the 
cross striations do not appear. Only the telophragmata are 
conspicuous. However, the fixation preserved the sarcosomes 
and they are seen to occur both in the dark dises (as Q-granules) 
and in the light dises (as J-granules). In alcohol-fixed tissue the 
granules are dissolved and so do not appear in stained sections 
(fig. 16). Their solution in alcohol, together with certain micro- 
chemical reactions, indicate that their chemical constitution is 
at least largely lipoid. The spherical J-granules are smaller than 
the oval Q-granules. The difference in shape may be due to 
lateral pressure exerted by the myofibrils on the larger originally 
spherical Q-granules. The simplest interpretation of the genetic 
relation and the segregation of these two varieties of sarcosomes 
is that the larger develop from the smaller, the latter originating 
along the telophragmata, probably by reason of the fact that the 
telophragmata furnish efficient pathways for the transfer of 
nutritive materials from the inter-fiber tissue spaces into the 
fiber. 
The location of the smaller J-granules close to the telophrag- 
mata accounts for the confusion of these granules with the 
constituent elements of the accessory discs, as well as with those 
of the contraction bands. Retzius?! claims that the accessory 
discs are actually aggregations of J-sarcosomes. Holmgren,° 
Heidenhain,’ and others claim that the contraction bands of 
contracted muscle also are simply aggregations of sarcosomes. 
That neither of these interpretations, however, is tenable is 
proved by the fact that in alcohol-fixed tissue, in which the 
sarcosomes have disappeared through solution, both accessory 
dises and contraction bands still occur. Moreover, both of these 
structures occur also in fibers in which no sarcosomes can be 
demonstrated. Both accessory disc and contraction band are, 
largely at least, composed of intramyofibrillar elements. The 
sarcosomes are interfibrillar bodies. 
The fiber illustrated in figure 15 is at an early phase of con- 
traction. The Q disc has lengthened and its myofibrillar elements 
