REPORT ON THE ACTINIARIA. 15 



the acontia. During maturity the reproductive organs lie in the supporting plate com- 

 posed of connective tissue. They form follicles of spermatozoa in the male, separate ova 

 in the female, and both together in hermaphrodite individuals ; the youngest ova lie in 

 the endodermal epithelium, which therefore represents the germinal layer, but even older 

 eggs — at least this has been observed in several species — are still connected with the 

 surface of the epithelium, either by means of a conical cord of protoplasm, or by means 

 of a bundle of epithelial cells, at whose base a process of the ovum passes transversely 

 through the supporting lamella. 



The mesenteric filaments occupy the free margins of the septa, beginning at the 

 upper end — at the oesophagus in the complete septa — and finishing tit a little distance from 

 the lower end. They are formed by the supporting lamella (PI. V. fig. 5) splitting at 

 the free margin into three lamina?, a middle and two lateral ; the former is covered by 

 a streak of epithelial cells, principally glandular, the latter bear extremely fine, small 

 ciliated cells. A visible cord of nervous fibres, which is entirely wanting in the ciliated 

 streaks, runs along the base of the glandular streak. The character of the filamenl 

 changes lower down, as the ciliated streaks with their supporting plate of connective 

 tissue disappear, and the median glandular streak only remains. 



The acontia (PL 1. figs. 4 and 5) are long filaments, kidney-shaped in transverse 

 section, which spring from the septa at a little distance from the lower end of the mesen- 

 teric filaments, lie coiled in the stomach during a state of rest, and are ejected through 

 special openings in the wall (cinclides), or through breaches in the wall, or through the 

 oral opening, when the animal is irritated. Their component parts are : (l) an axial band 

 of connective tissue, (2) an epithelium, chiefly composed of nematocysts, (3) nerves, and 

 (4) muscular fibres lying between the basal ends of the epithelial cells (PI. XII. fig. 10). 



Finally, there are special openings in the septa which connect the separate divisions of 

 the gastric space. There are two forms of such septal stomata. In nearly all Actinia? 

 we find openings which pierce the septa just where the latter touch the margin of the 

 mouth, and which form together a species of peristomial canal ; the upper part of these 

 openings is limited by the membrane of the oral disk, the remainder by the septa, so 

 that they are shut off from direct contact with the oesophagus. More rarely there are 

 other septal stomata, which lie close to the wall, about the junction of the first and 

 second thirds of the body (PL VII. fig. 12). 



I have hitherto described the anatomical conditions of the septa, as they may be 

 observed in the hexamerous Actiniae, and probably in all hexamerous corals. It would, 

 however, be very erroneous to assume that what has been said applies to all forms 

 hitherto included among the Hexacorallia ; we find, in fact, sundry variations, which I 

 shall place under five different categories, though I do not presume to say that these 

 exhaust all the variations presented in nature. 



Among the first group I place those Actinia? in which there are two pairs of directive 



