REPORT ON THE XENIIDAE COLLECTED BY DR WILLEY. 529 



Fig. i. Xenia Garciae, Bourne. One of the largest polyps of the colony, lent to me by 

 Mr G. C. Bourne. Note that the pinnules seen on viewing the tentacles from the outer 

 aspect arise close to the middle line, thus differing from those of the tentacles of X. Novae 

 Britanniae (compare Figs. 2 and 4). The specimen has been somewhat flattened by contact 

 with the sides of the bottle, x 15. 



Fig. 5. Xenia Novae Britanniae. Outer surface of a pinnule of a tentacle of a polyp, 

 showing the very numerous disc-like spicules present in the ectoderm. The spicules are often 

 in contact or even overlapping, x 190. 



Fig. 6. A portion of the body-wall of the same polyp 2 mm. below the bases of the 

 tentacles. Note that the spicules are much less numerous than in the pinnules, x 190. 



Fig. 7. Xenia Novae Britanniae. A thick longitudinal section through the middle of 

 the colony represented in Fig. 1. Tlie strongly convex area fi-om which the free parts of 

 the polyps arise may be seen. The coelentera of the polyps extend a considerable distance 

 into the stem, those of the large polyps extending to the base of the colony. On the dorsal 

 side of each polyp one of the dorsal mesenterial filaments (D. M. F.) is shown and may be 

 traced almost to the lower end of the coelenteron ; on the ventral side of the polyp the 

 thin edge of the ventral mesentery {V. II.) may be seen. These have been omitted for the 

 sake of clearness from polyps I, II, III, VI. On the right the section passes through a 

 bud or young polyp (I), the free part of which is 2 mm. long. The coelenteron of this polyp 

 extends inlj' a comparatively short distance into the stem. The stomodaeum {St.) of two 

 polyps (IV, V) is shown. The coelentera of the older polyps (IV, V, VI, VII) are 

 crowded with sperm sacs (.S'. 8.) in the portions situated in tlie upper part of the stem, 

 but they have been omitted from polyps V, VI. The superficial {Sup. Can.) and longitudinal 

 {Long. Can.) canal systems ; their relation to each other and to the coelentera of the polyps, 

 the plexus of canals at the base of the colony and the ectoderm (represented when seen in 

 section by a thick black line) are shown. The outer walls of the superficial canals are 

 thicker than the inner walls. Around each coelenteron there is a denser cylinder of mesogloea 

 {Mg. D.), this is shown only in polyps VI, VII, being represented by the darker tone round 

 these coelentera. Semi-diagrammatic x 6. 



PLATE LIII. 



Fig. 8. Xenia Novae Britanniae. A freehand section about '15 mm. thick passing through 

 the column of mesogloea between two adjacent coelentera. The thick dark bands (h'nd.) riglit 

 and left represent the endoderm of the coelentera. The denser cylinder of mesogloea {Mg. D.) 

 almost devoid of cells which encloses each coelenteron, with its surrounding ectoderm cells 

 {Ect. Ch.): the numerous strands of ectoderm cells (Ect. Str.) passing through llie othei' portions 

 of the mesogloea : the longitudinal canal {Long. Can.) with its branches {End. Can.) opening into 

 the coelentera : the superficial canal system {Sup. Can.) seen in section with its thicker outer 

 walls, and its relation to the longitudinal canal system {Long. Can.) may be seen, x 70. 



Fig. 9. Xenia Nocae Britanniae. A portion of the superficial canal .system whicli has 

 been stripped oS' the stem along with the ectoderm. The canals are nearly all in one j)lane 

 forming a close network about '1 mm. beneath the ectoderm, x 100. 



Fig. 10. Xenia umhellata. A iiud from the edge of the sunnnit of one of the stems. 

 The total length of the young polyp is 3'3 mm., the tentacles are 1'5 mm. long and show, 

 from the outer aspect, five or six pinnules on each side of the axis of the tentacle. Viewed 



