ZOOLOGY OF THE BERMUDAS. 121 



mesogloea are fairly developed, and immediately Lelow them 

 are to be seen, imbedded in the mesoglcea, peculiar granular 

 pale yellowish-green cells, the protoplasm of which, with the 

 exception of the nucleus, does not stain with carmine. Other-' 

 wise the mesogloea is homogeneous. The endoderm is thick, 

 and is richly supplied with zooxanthellee. In structure the 

 disc resembles the tentacles, possessing, like them, the peculiar 

 yellowish-green granular cells. 



The mesogloea of the stomatodseum is homogeneous. I can- 

 not make any statements as to the histology of the ectoderm of 

 this region, as it had macerated into a mass of a characteristic 

 appearance which cannot ensily be described. Transverse sec- 

 tions show that the gonidial groove, to which the macro or 

 ventral directives are attached, is very shallow, and indeed can 

 hardly be said to exist. 



The mesenteries are arranged on the microtypus.* Their 

 mesogloea is for the most part very thin but thickens towards 

 the base where it contains a canal. (PL 11, fig. 4, be.) A 

 second cnnal, circular in section and packed with cells, occurs 

 in the thin region, the mesogloea splitting to form its walls. 

 The muscle layers are only slightly developed. 



A very peculiar arrangement occurs in connection with the 

 mesenterial filaments of the perfect mesenteries. Immediately 

 below the stomatodseum the mesenterial filament is triradiate 

 (PI. 11, fig. 3), the central ray being short and stout, the lateral 

 rays longer and recurved. The epithehum covei'ing the cen- 

 tral ray and that face of t"he lateral rays which looks towards 

 it resembles in structure that of the stomatodseum. The outer 

 surface of the lateral rays is, however, covered with cells similar 

 to those which line the general surface of the mesentery. In a 

 section which passes through the stomatodseum a little above 

 its extremity, the intervals between the perfect mesenteries is 

 occupied by macerated tissue resembling the ectoderm of the 

 stomatodseum. Apparently, it lines the surfaces of the mesen- 



* See Erdmann, loc. eil. 



