REPORT ON THE XENIIDAE COLLECTED BY DR WILLEY. 517 



I'o mm. in breadth. The pinnules on the tentacle are beautifully and regularly arranged 

 in three rows on each side of the middle line of the tentacle. Each row contains 

 15 — 20 pinnules. Those near the base of the tentacle, the first four or six transverse 

 rows, are short rounded elevations or "warts" (Schenk) about "2 mm. — 3 mm. in length 

 and "15 mm. — '2 ram. in breadth, but the more distal ones are conical, thick, somewhat 

 pointed pinnules 5 mm. — 7 mm. long and "2 mm. — •25 mm. in diameter at their thickest 

 part. The middle line of the inner face of the tentacle is free from pinnules in the 

 proximal three-fourths of its length. The outer face of the tentacle is markedly convex. 



Round the edge of the polyp-bearing summit of the stem and also on other portions 

 of the summit between the bases of the larger polyps, young polyps in various stages of 

 development may be found. They are more numerous on the edge of the summit. Most 

 of them already show pinnules upon their tentacles, but those polyps the total length of 

 which does not exceed IS mm. (of which the tentacles form about -5 mm.) do not yet 

 show pinnules upon their tentacles. " 



The spicules are disc-shaped and numerous. They are generally oval in shape, 

 •018 mm. — ■02 mm. in length, about -Ol-smm. in breadth and OOC mm. in thickness. They 

 are whitish by reflected light and yellowish or yellowish-brown by transmitted light. 

 Spicules are moderately numerous in the stem, there are rather more in the body of the 

 polyp and still more on the outer face of the tentacles and pinnules. Spicules are less 

 numerous on the inner than on the outer face of the tentacles and pinnules. 



The stem is greyish green in colour and the polyps a much lighter shade of the 

 same colour. The tentacles are almost -white but have the slightest tinge of brown. 



Sperm sacs are present though not in very large numbers on the edges of the 

 ventral and lateral mesenteries of the larger polyps. The youngest sperm sacs form 

 small spherical projections at the side or free edge of the mesentery, each of which 

 consists of a follicle of endoderm cells within which is a thin lamina of mesogloea 

 enclosing the genital cell or the cells which have been produced by its division (see 

 PI. LIII. Fig. 14). The largest sperm sacs are -25 mm. in diameter and the spermatozoa 

 which they contain, though in an advanced stage of development, are not ripe. 



On carefully examining the mesenteries in sections, many of them are seen to bear 

 young ova, each of which is enclosed in an oval or pear-shaped follicle, in addition 

 to the sperm sacs. (See Fig. 14.) Each ovum has rather deeply staining, somewhat 

 granular protoplasm, scattered through which are several small cavities which, in life, 

 probably contained the yolk gi-anules of the ovum. The nucleus is large, clear and 

 vesicular, about •OI.t mm. in diameter, and contains a well-marked, spherical, deeply 

 staining nucleolus. These young ova are generally from 03 mm. to 'O-S mm. in diameter 

 but one or two attain a diameter of "08 mm. This colony is therefore hermaphrodite, but 

 it is evident that the male products will ripen first as they are in a much more advanced 

 stage of develo])ment than the ova. 



The stomodaeum of the larger polyps is 21 nun.— 2^2 mm. long. The goblet-like 

 cells to which reference has been made above may be seen among the ordinary 

 columnar cells in the ventral and lateral regions of the stomodaeum, especially near its 

 inner end. The siphonogl)-ph extends along the inner third (i.e. '7 nun. — •S mm.) of its 

 length. 



w. IV. «9 



