1907.] FROM THE CAPE YERDE ISLANDS. 501 



hydrotheca, and to these are attached strands supporting a flat- 

 tened disc-like portion at the base of the polyp. Such an attach- 

 ment, of course, makes the retraction of the polyp impossible. 

 The structure is identical with that which I have already 

 described and figured in the genus Hcdecium (Ritchie, 1907, 

 p. 525), except that in Hcdecium the basal disc rests upon the 

 perisarcal septum at the bottom of the cup, while here a consider- 

 able space intervenes between the two, ti-aversed by a narrow 

 strand of ccenosarc connecting the polyp with the common cceno- 

 sarc of the colony. I wovild draw attention to the seeming 

 inaccuracy of Hincks's figures (1868, pi. 45. figs. 2, 2') as regards 

 the relations between polyp and hydrotheca. The hydranths, 

 which are about 0'9 mm. in height, gradually increase in diameter 

 upwards from the basal disc, but exhibit no distal contraction 

 beneath the tentacles such as Hincks figures. The bases of the 

 tentacles, which number about 23, are connected by a web within 

 which the hypostome arises. A secondary hydrotheca, borne on 

 a relatively long peduncle, may arise from the lower portion of 

 the peduncle of a primary hydrotheca. 



Nematophores occur frequently but irregularly. There is 

 usually one on a peduncle, and sometimes one on an internode. 

 They are sessile, cup-shaped, with delicate walls and everted 

 margin, within which there is commonly a row of refringent dots. 

 To these, as in the hydrothecse, a basal coenosarcal disc is attached. 

 The sarcostyles correspond to those figured by Hincks (1868, 

 pi. 45), with thin walls bearing scattei'od cnidoblasts, and a glo- 

 bular head where large numbers of these offensive and defensive 

 cells are aggregated. When contracted, a sarcostyle measures 

 about 0'4 mm., while one which was extended measured 2'0 mm. 

 The cnidoblasts are narrowly oval, 17 y^ by 3 /i, and each contains a 

 thread 220 ^ long, ai-med near the base with a whorl of four barbs 

 in the form of a cross, distal to which are smaller barbs pointing 

 towards the tip of the thread and placed in four longitudinal 

 rows, each of which contains about nine gradually decreasing barbs 

 (Plate XXV. fig. 5). The cnidoblasts occur throughout almost 

 the whole colony, but are particularly common on the basal discs 

 of sarcostyle and polyp, and at the tips of the sarcostyles and of the 

 tentacles. 



Occasionally solitary hydrothecse and nematophores arise from 

 the hydrorhizal tube. 



The gonosome is not present. 



Locality. Porto Praya, Santiago, 10 fathoms ; 12th August, 

 1904. 



Family LafoIiid^. 



FiLBLLUM SERPENS (Hassall 1852). 



This species is represented by scanty specimens creeping on 

 a fragment of a Gymnoblast colony. In essential characters the 

 specimens agree with Hincks's description (1868), but they appear 

 to be of less robust growth, while the margins of the hydrothecae 



