9,]^g MKS. L. J. WILSMORE ON ZOANTHEiE FROM 



sides • on the entoccBle side it is continuous with the longitudinal muscle; 

 on the exocoele side it continues to about two-thirds the length o£ the basal 

 canal. A large basal canal is present, oval or circular in transverse sections 

 (PL 44. fio'. 6, h. c). In the upper part of the polyp, the basal canal widens 

 into a lono- slit which may be continuous through the width of the mesentery. 

 Duerden (8) has described the opposite condition in Z. pulchellus, where the 

 lono- slits occur at the base of the polyp. The endoderm of the mesenteries 

 from the capitulum to the lower end of the oesophagus contains very 

 numerous zooxanthellse. Below that point there are none present. As 

 zooxanthellse disappear from the endoderm of the column-wall at about the 

 same level, it follows that they are very abundant in the distal and rare in 

 the proximal part of the polyp. The reflected ectoderm of the mesenteries 

 closely resembles that of Z. Macgillivrayi as described by Haddon and 

 Shackleton (5). The digestive endoderm is very thick and encloses many 

 foreion granules as in Z.fios marinus (Sand 8); but here nematocysts also 

 occur, while the green granules of Z. fios marinus are rare. 



Gonads. — The species is hermaphrodite. Spermaria are present in abun- 

 dance in all five polyps examined. Three ova also occur in one polyp and a 

 single ovum in another. All four ova are ripe, of large size, and borne on 

 mesenteries which carry spermaria also. Nematocysts are frequently present 

 in the endoderm surrounding the spermaria. 



Parasites, — Two kinds of parasitic Protozoa are present in large numbers 

 in the swollen endoderm of the mesenteries. 



The unusually powerful sphincter muscle of Z. sandvicensis is its distin- 

 guishing characteristic. 



This is the more remarkable, since, as pointed out by Duerden (8), the 

 sphincter muscle in Pacific species is, on the whole, much less developed 

 than in West Indian species. 



In other anatomical points Z. sandvicensis comes nearest to Z. flos marinus 

 described by Duerden from the West Indies, and to Z. chiercJme, von Heider 

 (7). The locality of the latter is unknown. ■ 



It is, however, easily distinguished from these two species by, among other 

 points, the sphincter muscle, number and character of mesenteries, structure 

 of column-wall and ectoderm, and form of coenenchyme. 



ZOANTHUS SIMILIS, sp. n. (Pls. 43, 44. figs. 7-10.) 



Form (PI. 43. fig. 7). — This colony closely resembles that of Z. sand- 

 vicensis in external appearance, but the polyps are distinctly smaller and more 

 slender. The growth of the coenenchyme takes place as in Z. sandvicensis by 

 broad bands. Several are present measuring 12-15 mm. in length, and 5-7 

 mm. in wddth. There is a large growth of ccBuenchyme at one side (PI. 43. 

 fig. 7), on which some young polyps are developing at long intervals. 



