690 Reports on the Zoological Collections made in Torres Straits, 1888-1889. 



ri;«k 



Fie. 1.- 



-Gemmaria mutuhi. Transverse 

 section of body- wall. 



The 



also present. Cell enclosures consisting for the most part of lacunse are very 

 nnmerous in the mesogloea. There is no 

 regular series of canals or of lacunae lying 

 at the union of each mesentery with the 

 body-Avall, such as we have described for 

 G. macmurrichi. In some parts of the wall, 

 the lacunjB lie so close together beneath the 

 incrustations, as to suggest an interrupted 

 encircling sinus ; but for the most part they 

 are irregularly scattered through the meso- 

 gloea. Zooxanthellse are found in many of 

 these lacunae. The endoderm forms a uniform 



layer of moderate thickness in which zooxanthellae are very numerous, 

 muscular layer is well developed. 



Sphincter muscle. — The usual single mesogloeal sphincter muscle is present. 



Disc and tentacles. — As in the body-wall, zooxanthell^ are present in both 

 ectoderm and endoderm in this species, though they are much less abundant in 

 the former than in the latter layer. The ectodermal muscular layer is rather 

 weak. In both these features it will be seen that G. mutuJci differs from G. mac- 

 murrichi, and resembles M^Murrich's two West Indian species. The mesogloea of 

 the disc in this species also contains cell enclosures. 



OEsophagus. — The groove is well marked, and of the truncated form described 

 and figured by M^Murrich for G. isolata (1889 A, p. 66, PL iv., fig. 20). 



Mesenteries. — The mesenteries have the usual brachycnemic arrangement. The 

 mesogloea is fairly well developed ; the musculature is rather weak. Each 

 mesentery contains a single basal canal, which does not divide in the oesophageal 

 region as in G. macmurrichi, but runs up vertically from the base of the polyp 

 almost to the disc. The tissues in the lower part of the coelenteron in our 

 specimen are unfortunately not sufficiently well preserved for us to give details 

 regarding the mesenterial filaments. 



Gonads. — Numerous ripe sperm cells are present in the coelenteron of the 

 specimen cut by us. 



Externally this species may be distinguished from G. macmurrichi by its 

 shorter, more stumpy form. Anatomically it differs from G. macmurrichi in 

 the presence of numerous zooxanthellae, in the continuous ectoderm, and in 

 various other points, which will be seen by comparing our description of the two 

 species. Outwardly, G. mutuki may also be readily distinguished from the two 

 West Indian species, but in several anatomical points, referred to above, it seems 

 to agree more nearly with them than with G. macmurrichi. 



