674 Reports on the Zoological Collections made in Torres Straits^ 1888-1889. 



kuown it will generally be possible to identify other specimens belonging to that 

 species by external characters only. Owing to the incrusted nature of most of the 

 Zoanthe^ it is very difficult to get satisfactory sections, and for the same reason 

 spirit specimens are often apt to be badly preserved for histological purposes. 



It is not unfair to point out that the disorder which has occm-red in this group 

 is also partially due to the fact that many zoologists have not paid due regard to 

 the generally recognised rules of zoological nomenclature, and have not taken the 

 trouble to thi'ash out the synonymy ; and some have identified certain forms with 

 pre-existing species in a rather reckless manner. 



Owing to the lack of salient external characters, which could be observed in 

 preserved specimens, we have not been able to give diagnostic names to most of 

 the species, and we have consequently associated them with the names of zoologists 

 who have collected in Torres Straits, or who have studied the group. The types 

 of the species have been given to the British Museum, in which institution will 

 also be found a complete set of slides illustrating the anatomy of all the forms 

 described in this and in the preceding Memoir. 



CLASSIFICATION OF THE GEOUP. 

 ZOANTHE^. 



Actiniae with numerous perfect and imperfect mesenteries, and two pairs of 

 directive mesenteries, of which the sulcar are perfect and the sulcular are imperfect. 

 A pair of mesenteries occur on each side of the sulcular directives, of which the 

 sulcular moiety is jDerfect and its sulcar complement is imperfect ; a similar second 

 pair occurs in one section of the group (Brachycneminse), or the second pair may 

 be composed of two perfect mesenteries (Macrocneminse). In the remaining pairs 

 of mesenteries, of both divisions, this order is reversed, so that the perfect mesentery 

 is sulcar and the imperfect is sulcular. The latter series of mesenteries are bilateral 

 as regards the polyp, and arise independently {i.e. neither in pairs nor symmetri- 

 cally on each side) in the exocoele on each side of the sulcar directives, in such a 

 manner that the sulcular are the oldest, and the sulcar the youngest. Only the 

 perfect mesenteries are fertile, or bear mesenterial filaments. A single sulcar 

 oesophageal groove is present ; the mesogloea of the body-wall is traversed by 

 irregularly branching ectodermal canals, or by scattered groups of cells ; the body- 

 wall is usually incrusted with foreign particles. The polyps are generally grouped 

 in colonies connected by a coenenchyme, the coelenteron of each polyp communicat- 

 ing with that of the other members of the colony by means of basal endodermal 

 canals. 



