REPORT ON THE XENIIDAE COLLECTED BY DR WILLEY. 523 



I have added a table of measurements and of the chief characters used in the 

 diagnosis of all the other known species of Xenia in the hope that it may be useful to 

 those who may work over the family in the future. Following Schenk the family 

 may be divided into three portions. 



I. The tentacles of the polyps of the species forming this division bear more 

 or less elongated conical pinnules generally placed in two series of three rows in 

 each. Most species of Xenia belong to this division. (10 species.) 



II. Each tentacle bears two types of pinnules, (1) smaller short round pinnules 

 or "warts" (Schenk) at the base of the tentacle, and (2) more typical elongated 

 pinnules on the more distal portion of the tentacle. (4 species.) 



III. The pinnules upon the tentacles are all small conical or rounded warts 

 arranged either in irregular rows or scattered over the whole face of the tentacle. 

 (2 species.) 



The numbers enclosed within parentheses in the table have been added by me 



to the authors' descriptions, being taken either from the published figures or in the 



cases of X. Garciae and X. coerulea from the original specimens kindly lent to me 

 by Mr G. C. Bourne. 



GENERAL INTERNAL ANATOMY. 



Sections of the stem of each, and the polyps of some, of the species above 



described have been cut and examined. As all the species agree moderately closely 



with A''. Hicksoni (Ashworth, 1899) in the main features of their anatomy this portion 

 of the report will be somewhat brief. 



Stomodaeum and Mesenterial Filaments. 



In many of the polyps the mouth is situated at the bottom of a slight depres- 

 sion '2 mm. — 4 mm. in depth, which has been produced by partial contraction of the 

 oral disc. The mouth leads into the stomodaeum, which is generally compressed 

 laterally, though in one species {X. viridis) it is almost circular in transverse section. 

 The stomodaeum of the fully developed polyps varies in length from "8 mm. — 2-2 mm. in 

 the various species. The length of the stomodaeum is doubtless related in some degree 

 to the length of the free portion of the polyp as in those species which possess short 

 polyps, e.g. X. crassa and X. Novae Bvitaimiae, in which the bodies of the polyps are 

 only about 3 mm. in length, the stomodaeum is only '8 nun. — •!• nun. lony. The length 

 of the stomodaeum does not however appear to entirely depend on the length of the 

 polyp, as in X. viridis, in which the polyps are comparatively short (the body measures 

 4 mm. — 6 mm.), the stomodaeum is 2-1 mm. — 2-2 mm. long, while in A', inembranacea. in 

 polyps the bodies of which are 10 mm. — 11 mm. long the stomoilacum is only 1"7 mm. — 

 1"9 mm. long. 



In the stomodaeum of the polyps of Z. viridis and A'. Novae Britanniae, the duly two 

 species from this collection which have been cut into thin transverse sections, a ventral 

 groove or siphonoglyph is present, the cells of the lower third or two-fifths of which 

 bear flagella. 



