REPORT ON THE XENIIDAE COLLECTED BY DR WILLEY. 513 



are yellowish-brown. They are present in moderate numbers in the stem, but are 

 more numerous in the body of the polyp and in the tentacles, and still more 

 numerous on the outer face of the pinnules, but there are comparative!}- few on the 

 inner face of the pinnules. 



The specimen is dark brown, its colour being due partly to the spicules and to 

 the contained zooxanthellae and partly to the colour of the soft tissues. 



The stomodaeum of the lai-ger polyps is 1"7 mm. — 1'9 mm. in length. 



On examining in spirit the surface of the ectoderm of the polyps, numerous 

 minute refringent oval bodies are clearly visible. Most of these bodies are imbedded 

 in, and their long axes are at right angles to the free surface of, the ectoderm. 

 These are very probably nematocysts. They are '008 mm. — '009 mm. in length and 

 ■002.5 mm. in diameter, thus agreeing very closely with the nematocysts of X. Hicksoni 

 (1S99, p. 258), which are "008 mm. long and "002 mm. — '003 mm. in diameter. 



The specimen is apparently a male, but the sperm sacs are very few in number 

 and very small in size, and are obviously in an early stage of development. They 

 are rather oval and the largest measure only about '05 mm. along their greater 

 diameter. 



Habitat. New Britain. 



This specimen agrees with the description given by Schenk of X. rnembi-anacea. 

 The general characters of the stem and polyps agree with the diagnosis of the species 

 very well indeed ; the polyps and tentacles of Dr Willey's specimen are rather larger 

 than those of the type specimen, but their general proportions are almost identical. 

 Schenk's species derived its name from the basal membranous expanse which bound 

 together the bases of the stems. A similar basal membrane is present in Dr Wille3f's 

 specimen but is developed to a less extent, probably owing to the dififerent mode of 

 attachment of the colony. Schenk's specimen was attached to a sandy (and probably flat) 

 substratum which would offer favourable opportunities for the formation of the basal 

 membrane. 



Previously recorded from Ternate (Moluccas). 



XENIA UMBELLATA. Savigny. 



There are three colonies referable to this species. 



I. The basal portion of the largest colony encrusts a piece of weathered coral 

 rock. From this rather thick membranous base (which is 2 mm. — 3 mm. in thick- 

 ness) three stout fleshy stems arise, the largest of which is about 33 mm. high 

 and 30 mm. x 15 mm. at the base. At a distance of about 10 mm. from the summit 

 this stem is divided into a larger and a smaller branch by a deep fissure. The stenj 

 next in point of size is 25 mm. long and measures 15 mm. x 15 mm. at the base. 

 The smallest of the three stems of this colony is 20 mm. high and 15 mm. x 13 mm. at 

 the base. All the stems increase slightly in diameter as they ascend. The summit 

 of each stem is a flat or slightly convex area from which the polyps arise. 



II. The second colony is also attached at the base to a piece of worn coral 

 rock. It consists of a single stout fleshy stem about 25 mm. high and 23 x 13 mm. 



