MUSCLE ATTACHMENTS AND EPIDERM IN CRAYFISH 383 



The muscles are attached to the epithelial cells and not directly 

 to the tendon fibers according to List, Viallanes, Vitzou and 

 Weisman. Stamm declares that the muscles are inserted to the 

 basement membrane and that there are no fibrils passing through 

 the membrane. Bertkau (in spiders) finds muscle fibers to be 

 continuous with the tendon fibers, but he can always see a distinct 

 dividing line between the epithelium and the muscle. 



Leydig, Duboscq and Snethlage declare that the sarcoplasm is 

 continuous with the protoplasm of the ectodermal epithelial cells, 

 but this is denied by Holmgren, excepting for the vagina of Sar- 

 cophaga, where he found direct continuity between chitin matrix 

 cells and the sarcoglia of muscles. This is explained as being the 

 persisting embryonic connection between ectoderm and mesoderm 

 which was described by Heatcote. 



Tendon fibers and muscle fibers are directly continuous with 

 one another according to Claus, Duboscq, Leydig, Lecaillon and 

 Henneguy. but Riley declares that there is a splicing or fusion of 

 the muscle fibers into the tendon fibers and no direct continuity 

 between the two. 



Many authors believe that the tendon fibrils are merely pro- 

 longations of the muscle cells. Frenzel, Nicolas, Ide, Pantel, 

 Hecht and Holmgren locate the tendon fibers between the epithe- 

 lial cells instead of within them. As the muscles approach the 

 epithelium they are resolved into fine bundles of fibrils which pass 

 between the epithelial cells to be inserted directly into the chitin. 

 According to another scheme of Holmgren's the muscle fibrils 

 penetrate the epithelial cells and are then inserted to the chitin. 

 Nowikoff and Snethlage believe that both tendon and muscle 

 are developed from ectoderm, so the continuity of the two types 

 of fibrils is easily explained. Emmel found that in the regenerat- 

 ing lobster claw the new tendon fibrils are merely the non-striated 

 ends of the muscle fibrils which are developed in an ectodermal 

 syncytium. The striations may continue as far as the level of 

 of the chit in-forming outer later of this syncytium. 



The tendon fibers are described by Claus as being very coarse, 

 while Henneguy states that they are identical in appearance 

 with fibrils in other parts of the epidermis where there are no 



