REPORT ON THE ANTIPATHARIA. 205 



They are contained within semi-fibrous capsules, which appear to be attached to the 

 mesoglcea, but I am uncertain whether they are derived from it. The mesogloea does 

 not stain in borax-carmine in any of the Antipathinse yet examined, whilst the capsule 

 surrounding each ovum assumes a distinct carmine tint. It may therefore possibly 

 prove to be a true vitelline membrane. The mesogloea of Hexactiniae has been shown 

 by R. Hertwig to stain red in picro-carmine, but material preserved for a long time in 

 spirit does not apparently take the stain so well. 



Leiopathes glaberrima. 



The zooids of Leiopathes glaberrima are very unequal in size, owing to the formation 

 of new zooids at irregular intervals by a process of budding. An elongation of the 

 zooid in the transverse axis is never well marked. Apparently the sagittal tentacles, 

 which are larger than the others, sink to a lower level in older individuals. In such 

 cases horizontal sections taken at a point above the insertion of the sagittal tentacles are 

 oblong, the greatest diameter corresponding with the transverse axis (cf. figs. 1, 2 and 3, 

 p. 37). The fully-developed zooids are arranged about four to a centimetre, but in cases 

 where young individuals are interposed between the adults there may be five or six to a 

 centimetre. In large degenerate zooids the ectoderm may be 0'4 mm. thick, and the cells 

 composing it quite indistinct, whilst the entoderm remains quite normal. Subsequently 

 the wdiole of the zooidal tissues become degenerate, and form oval bead-like swellings of 

 the ccenenchyma, which are about 1 mm. in diameter. These are first recognisable at a 

 point from 2 to 3 '5 cm. from the apex of a branchlet, and form oval thickenings, four or 

 five of which are arranged to a centimetre. Possibly the early atrophy of functional 

 zooids may account for the fact that the spines of this species are confined to the more 

 slender portions of the sclerenchyma. 



Ectoderm. — The ectoderm of the tentacles is raised into small oval papdlse, the long- 

 axes of which are arranged transversely. In longitudinal sections of a tentacle these 

 papillae appear as irregular crenations (PL XV. fig. 3). Each crenation is occupied by 

 a fan-shaped bundle of nematocysts, beneath which elongate thread-like cells extend to 

 the base of the layer. Each battery in section is from 0"02 to 0'04 cm. broad at the 

 surface, but becomes rapidly contracted towards the middle, and is dilated again near 

 the base of the layer. The nematocysts are - 02 to 0'03 mm. long, and are broader at ' 

 their distal, than at their proximal, ends. A number of the thread-like cells beneath 

 them have large oval nuclei which stain deeply ; others which are more slender are 

 perhaps sensory in function. The space between adjoining batteries of nematocysts is 

 occupied by a group of hyaline gland cells. The glandular patches are usually more or 

 less oval in outline, and have a diameter of 0'02 to 0'04 mm. near the middle. The clusters 

 rapidly taper towards the surface of the ectoderm, and open on the narrow transverse 



