SEXUAL CHARACTERS—ELASMOBRANCH FISHES 263 
Attached to the siphon on its dorsal side is a large muscle 
band, which has already been alluded to in Scyllium. It is 
composed of fibers which are more markedly striped than any I 
have hitherto observed in the Vertebrata, and, in addition, 
possess two peculiarities: they exhibit ‘nodes’ where presumably 
one muscle cell adheres to its neighbor, the distance between 
the nodes decreasing in an appreciable manner as one approaches 
FAR ae 
Fig. 11 Raia circularis. A., a diagram; B., a horizontal section through the 
six posterior components of the clasper gland (haemalum-eosin). 1, 2, 3, 4, 4, 6, 
the six posterior components of the gland numbered from the posterior end; 
P., the papilla of the sixth component; m., muscle; S., siphon. 
the point of insertion of the whole fiber on the siphon wall, so 
that the final internodes are small, and the terminal section ends 
bluntly in a digitate manner, subserving thereby functions 
analogous with a tendon (fig. 12). The point of origin of the 
siphon muscle is the pelvic girdle (pubic bar), and such a muscu- 
lature suggests that it may be a retractor muscle for the pro- 
trusion and invagination of the siphon and its gland, although 
