438 G. H. PARKER AND E. G. TITUS 



1. The longitudinal muscle of the tentacle is an elongated 

 conical sheet of muscle that forms the deepest layer of the ecto- 

 derm and is in direct contact with the supporting lamella of 

 the tentacle. Its fibers course lengthwise in the grooves and 

 on the crest-like elevations that extend up and down the outer 

 surface of the lamella. They are more abundant and larger 

 than the fibers of the circular muscle of the tentacle, but show 

 no special grouping, being uniformly distributed around the 

 whole tentacle (Hert^lg, 79-80, p. 488). 



2. The circular muscle of the tentacles is also an elongated 

 conical sheet lying next the supporting lamella of that organ 

 on its entodermic side (Hertwdg, '79-80, p. 492). In this mus-, 

 cle the fibers take a circular course, and are fewer in number 

 and finer than in the longitudinal muscle. They show no special 

 differentiation except at the base of the tentacle, where there is 

 a slight tendency to form a sphincter. 



3. The radial muscle of the oral disc is made up of irregular 

 dense bundles of ectodermic fibers more or less imbedded in 

 the mesogloea of the disc. They radiate from the region of 

 the mouth outward toward the periphery of the disc making 

 their way between the bases of the tentacles (Hertwig, '79-80, 

 p. 489). 



4. The circular muscle of the oral disc is a flat muscular ring, 

 whose fibers take a course concentric with the mouth and are 

 often much involved in the supporting lamella of the disc on 

 its entodermic side. (Hertwig, '79-80, p. 495). 



5. The circular muscle of the oesophagus is a cylindrical 

 muscle ensheathing the oesophagus on its entodermic face (Hert- 

 wig, '79-80, p. 517). It is not very strongly developed and its 

 fibers, which take a circular course, are more or less interrupted 

 where the complete mesenteries are attached to the oesophageal 

 wall. 



6. The circular muscle of the pedal disc is a system of fibers 

 concentric with the disc and more or less imbedded as circular 

 bundles in the inner face of the supporting lamella of the disc. 

 This muscle is a well developed, vigorous organ (Carlgren, '93, 

 p. 105). 



