14 THE VOYAGE OF H.M.S. CHALLENGER. 



slightly arborescent, as is shown in PI. II. fig. 2, and arranged close to one another 

 like the leaves of a book. At the free edge of the pleat the musculature is 

 interrupted, since here the fibres of the mesoglcea, which serve as foundation for 

 the muscle-pleat, radiate into the epithelium. For some distance they are united 

 in a bundle ; they then part, and each fibre individually tends in the direction of the 

 epithelial surface. The nerve-fibre layer is consequently pierced by fine fibrils, arranged 

 parallel to and at equal distances from one another. I would have gladly determined 

 how far the connective tissue fibres reach, and whether they are connected with indi- 

 vidual epithelial cells or not ; but in thin sections I could only follow them into the 

 dim granular striated layer of epithelial cells, in which they were no longer distin- 

 guishable from other fibres. Attempts to exhibit the isolated fibres by brushing and 

 agitating thin sections, or by maceration in alkali, yielded no result ; and staining with 

 picrocarmine was also unsuccessful. The latter generally stains the mesoglceal struc- 

 tures of a deep red, and is therefore peculiarly adapted for exhibiting the mesoglceal 

 lamina which carries the muscles, but it refuses to differentiate the fibrils. The red 

 tint is therefore only seen to extend so far as is expressed in the figure by shading ; 

 the fibrils probably do not stain, but only the cement substance uniting them. The 

 condition here described may be followed on to the oral disc, inasmuch as the sup- 

 porting laminae of the muscle pleats here also run out in fibres, and the individual 

 fibres radiate to the epithelium. I have only further to remark that radial furrows, 

 shallow and slightly expressed, run from the edge of the oral opening towards the 

 tentacles. 



The stoniatodaeum, in the only specimen which I could examine, was evaginated, 

 and consequently so tightly stretched that even the siphonoglyphes were almost 

 smoothed out, and hardly recognisable. 



The mesenteries agree in number with the tentacles ; all reach the stomatodseum, 

 and bear generative organs. The younger mesenteries touch the stomatodseum some- 

 what further back, and are in other respects less developed than the older ; but their 

 generative organs are more voluminous than those of the first and second orders. 

 Stomata in the mesenteries, and acontia, I have not been able to recognise. 



Family 3, Actinidje, A. Andres. 

 Antheadw, Herhvig. 



Genus Hormathia, Gosse. 



Actinias with broad diffuse endodermal sphincter ; smooth thin body-wall, and 

 parietal spherules (i.e. marginal spherules placed on the body-wall). 



