No. 2.] MORPHOLOGY OF THE ACTINOZOA. 145 



the same structure as in the disc, except that the fibres near 

 the base of the lamellae are much smaller in diameter than 

 those which cover the greater portion of their surface. I have 

 not been able to discover the slightest trace of circular muscles 

 intermingled with the longitudinal, as Danielssen describes in 

 C. borealis, Danl. 



The mesogloea presents the same structure here as on the 

 disc. The muscle lamellae are prolonged at their free edges 

 into numerous fine branching processes, which traverse the 

 nerve layer, and pass up into the epithelial region of the ec- 

 toderm. Continuations of the epithelial cells also traverse the 

 nerve layer, and pass down between the muscle lamellae, and 

 are perhaps nervous, or partly nervous, and partly the basal 

 portions of the " Stiitzzellen." A circular musculature is 

 present on the inner surface of the mesogloea. 



(c) The St07natodceum. 



As already stated, the surface of the stomatodasum is raised 

 into numerous longitudinal folds, each of which corresponds to 

 an interval between two mesenteries (Fig. 7). The ectodermal 

 surface of the mesogloea is raised into slight ridges correspond- 

 ing to the folds of the ectoderm, and is provided with short 

 lamellae supporting the longitudinal muscle fibres, which have 

 a much smaller diameter in this region than elsewhere. The 

 delicate branching processes from the mesogloeal lamellae are 

 very evident (Fig. 7), especially those which arise from the 

 muscle processes covering the ridges. They can be traced for 

 some distance up into the ectodermal epithelium, forming 

 supports for its cells. 



The epithelial and nerve layers have the same structure and 

 histological characters as in C. membranaceus. Circular muscles 

 occur in the endoderm. 



(d) The Mesenteries. 



The disc in CerianthiLS being funnel-shaped, a section made 

 transversely through the column wall in its uppermost part will 

 cut the disc tangentially (though slightly obliquely to its thick- 

 ness) and the marginal angles of the mesenteries obliquely ; 

 that is to say, the section of the mesenteries shows their actual 

 thickness, but it is at an angle to both their length and breadth. 



