REPORT ON THE ANTIPATHARIA. 203 



the portion of the ccelenteron beneath the ovary, and in some sections are seen to be 

 united to the lower lateral angle of the ovarian mesoglcea. 



Ectoderm. — The ectoderm varies from 0'04 to - 06 mm. in thickness, and differs con- 

 siderably in structure from that of Antipathella. The surface of the ectoderm is raised 

 into innumerable small rounded papilla?, varying from 0*09 to G'117 mm. in diameter. 

 Longitudinal sections of a tentacle taken near the surface (PI. XIII. fig. 9), show that the 

 centre of each papilla consists of a battery of nematocysts, whilst the margin and the 

 depression between adjoining papillae is occupied by gland cells. These papillae are most 

 marked on the tentacles and upper portion of the polyp. The surface of the ectoderm 

 becomes smooth towards the base of a polyp. The nematocysts vary from 15 /x to 24 /a in 

 length and have a diameter of about 1"5 ju, ; they are similar to those of Antipathella in 

 all respects excepting size. The gland cells, on the other hand, are quite different. In 

 longitudinal sections of a tentacle (PL XIV. fig. 5), they are seen to occupy the depres- 

 sions between adjoining papillae, but never extend to the base of the layer, as in Anti- 

 pathella, The depressions in which the gland cells are situated are usually much more 

 marked than is shown in the figure. The gland cells vary from 23 /j. to 25 p in length 

 in the tentacles, and are filled with dense refractive granules. All the ectodermal glands 

 of this species are apparently of the granular type. 



The fibrous (" sensory") layer of the ectoderm is of considerable thickness (23 fi to 

 26 /a). The fibres are very numerous and delicate, and extend from the bases of the 

 nematocysts and gland cells to the mesoglcea. At the base of the layer a number of 

 ganglia occur (PL XIV. fig. 5, ga), which appear more numerous than in Antipathella. 

 Some of the fibres beneath the batteries of nematocysts present two or three bead-like 

 thickenings as is figured by Jourdan for the Actiniaria. 



The ectodermal muscular layer is well developed in Antipathes dichotoma, and con- 

 sists of a single row of longitudinal fibres applied to the smooth surface of the mesogloea. 

 In transverse sections of a tentacle the elongate slender fibres constituting the greater 

 portion of the middle layer of the ectoderm appear to be continuous with the specialised 

 longitudinal fibres of the muscular layer. A similar appearance is presented in the 

 ectoderm of the base (PL XIV. fig. 6,/). The ectodermal musculature does not apparently 

 attain so much importance in the stomodaeum as in other parts. 



In the ccenenchyma, consisting of the fused bases of the polyps at the back of a branch, 

 there is an almost total absence of nematocysts. In sagittal sections they are seen to 

 become less numerous on the body-wall, and towards the base they usually disappear 

 altogether. The gland cells, on the other hand, increase considerably in number, and 

 ultimately constitute the greater portion of the surface ectoderm. They are here, however, 

 more irregular in size and shape, and some do not reach the surface. The slender fibres 

 appear to be more numerous, and some of them may be clearly seen to reach the surface 

 of the ectoderm. Near the base of the fibrous layer numerous irregular groups of granules 



