578 



DR J. STUART THOMSON ON 



Capnella gilchristi, n. sp. 



Plate II. fig. 11 ; PI. IV. figs. 40 o-c. 



The colony consists of a basal trunk, and an upper part bearing the polyps, which 

 are in berry-like clusters or lobes. These lobes are frequently subdivided into smaller 

 lobes. The lobes are 20-25 in number, and they lie close to one another, not being so 

 much separated as in Capnella rugosa, Kiikenthal. The lobes are situated on short 

 stalks, about 1 mm. in length. The colour of the specimens is dark brown. The polyps 

 are not retractile, but the tentacles can be completely withdrawn within the stomodeeal 

 part. The surface of the trunk is marked at intervals by irregular, somewhat circular 

 lines or wrinkles. The dimensions of the specimens are as follows : 



The polyps with retracted tentacles measure approximately 2 mm. in length and 

 1 -5 mm. in breadth. The calyx is apparently absent. The spicules of the polyps are not 

 arranged in " Stiitzbiindel," though the heads of foliaceous clubs project on the convex 

 surface. The arrangement of the polyp spicules is as follows : Firstly, from long 

 spindles or clubs, which are situated on the basal part of the polyp, a longitudional row 

 of spicules (also spindles or clubs) runs up the more convex side of the polyp to the 

 apex, projecting a little externally and giving a very rough, sharp, and stony texture to 

 this part. Secondly, on the concave side of the polyp, smaller spicules are seen, which 

 also project on the surface, but not so much. The accompanying figure gives a better 

 idea of this than any verbal description. 



Sections show anatomical features fairly similar to those of Capnella rugosa, 

 Kiikenthal, but the spicules are differently arranged. The dorsal and ventral inter- 

 mesenterial cavities are smaller than the other six, thus producing a tendency towards 

 bilateral symmetry. The siphonoglyphe is ciliated, and directed towards the exterior 

 or away from the centre of the colony. The wall of the stomodseal tube is thick, and 

 apparently does not contain spicules. The muscles are poorly developed, but the 

 mesenterial filaments are fairly large and prominent. 



The canals of the trunk are larger towards the centre. The rind has more spicules 

 than the internal part, but the canals of the latter are surrounded by a fairly abundant 

 mass of spicules. 



