MUSCLE ATTACHMENTS AND EPIDERM IN CRAYFISH 389 



dermal fibers. There is no cuticular basement membrane, such 

 as is described by McMurrich, Holmgren and Emmel, and no 

 connective tissue ' Grenzlamella ' as stated by Claus and Schneider, 

 although fibers from the supporting tissue may enter into the 

 fibrous layer in the basal portion of the hypodermis. 



Where the layer of basal fibers is well developed it may pass 

 between the muscle and tendon fibrils in the region of muscle 

 attachment (figs. 1 and 2), or it may bend downwards and run 

 along the surface of the muscle or continue for some distance 

 between the muscles (fig. 3) . A horizontal layer of fibers between 

 the muscles and their tendon fibers may also be produced by con- 

 tinuous branches of the tendon fibers themselves (fig. 5). This 

 is probably what Snethlage saw when he stated that between the 

 muscles and their tendon fibrils an apparent basement membrane 

 is produced by anastomosing muscle fibrils and pigment granules. 

 Small, highly refractive pigment granules are also found in the 

 crayfish in this region, but they are seen only when the light is 

 cut down. For the sake of clearness they have been omitted 

 from the drawings. 



Figures 1 and 4 show that bundles of fibers are not limited to 

 the basal layer of horizontal fibers. At the outer border of the 

 hypodermis these bundles are resolved into their individual fibers 

 which spread out fan-shaped and probably penetrate the chitin. 

 In the present investigation no attempt was made to determine 

 the relation of the fibrils to the chitin, but many authors state 

 that they are continued into the chitin. 



Close study of the tendon fibers (T. F., figs. 1, 2, 3, 5) shows 

 that they are coarse, straight bundles of fibrils which seem to be 

 identical with those which are found in other regions of the hypo- 

 dermis. This is in accord with the findings of Henneguy, but 

 is contrary to Emmel. The outer ends of the tendon fibers, where 

 they are attached to the chitin, are frequently spread out in such 

 a way that they form a fan-shaped figure in sections. This is 

 seen especially well in the isolated smaller bundles of fibers such 

 as are shown in figure 1, T. F.' and on the left of figure 2. Here 

 one sees that the fibrils correspond in size, structure and staining 

 reactions to the supporting fibrils in other regions of the hypoder- 



