552 



OLWEN M. EEES. 



The specimen contained a large amount of mucus, this caused the 

 tissues to contract and become very hard in xylol. The specimen had 

 become very much contracted ; for these reasons I am unable to give a 

 full description of the species. The mesenteries are arranged in two 

 cycles, 36+36=72. The incomplete mesenteries are unevenly developed, 

 some appear as slight projections into the coelenteron, others are larger 

 and have produced many muscle folds. 



The mesenteries (Fig. 16) possess a very long retractor muscle with a 

 large number of short folds. The curious fact about this muscle is that it 

 faces the intramesenterial space or exocoele instead of the intermesenterial 

 space or endocoele, as is commonly found in Actinians. The longitudinal 

 muscle of the directives faces the intermesenterial space. Near the 

 proximial end of the mesentery lies the parieto-basilar muscle, which arises 

 as a stout projection on the side away from the retractor muscle. It gives 

 off a large number of folds which are longer than those of the retractor 

 muscle, they have a somewhat reticulate appearance when examined 

 under the high power of the microscope. The mesogloea is fibrous and 

 has a number of cavities of irregular shapes. The wall of the oesophagus 

 is raised into a number of lobes. There is one oesophageal groove corre- 

 sponding to the pair of directive mesenteries present. 



The body-wall is strong, the mesogloea forming a thicker layer than 

 the ectoderm. The latter is raised into a large number of folds, each 

 being supported by a process of mesogloea. 



This species is extremely rare, and British specimens were not available. 

 One specimen of Aureliania regalis was, however, most kindly sent by 

 Monsieur Louis Fage from the laboratory at Banyuls-sur-Mer, and it is 

 this specimen which has been anatomised and is described above. 



INDEX TO LETTERING. 



ect., ectoderm. 



ect. m., ectodermal muscle. 



end., endoderm. 



end. m., endodermal muscle. 



end. sp. m., endodermal sphincter 



muscle, 

 g., granules, 

 gl. c, gland cell. 



mes., mesogloea. 



mu., mucus. 



n.l., nerve layer. 



nem., nematocyst. 



pb. m., parieto-basilar muscle. 



r.m., retractor muscle. 



sph., sphincter. 



zoox., zooxanthelke. 



