304 MR. H. N. MOSELEY ON DEEP-SEA ACTINIARIA 



cold water of the deep sea. A Cerianthus occurs at the Island of Mactan, opposite Zehu, 

 in the Philippines, which has a tube 1 foot 4 inches long, the animal itself being 

 6 inches in length. I found this Cerianthus abundant in water only 1 foot in depth at low 

 tide about the reefs, with its tentacles expanded, in the full glare of the tropical sun. 

 Yet a species of the same genus can exist at a depth of three miles, where no solar 

 light exists, and in water at a temperature close to freezing-point. 



The occurrence of a Nematoid worm in abundance in the substance of the tube of the 

 Cerianthus at this great depth is a very striking fact. The fact that some of the deep- 

 sea Actinias still retain a vivid colouring in the dark depths is also of great interest and 

 importance. I have dwelt on such facts and on the colouring-matters of deep-sea 

 animals generally elsewhere*. The usual absence of rocks or other objects offering a 

 wide surface for attachment seems to have led to the development of the peculiar elon- 

 gated base in Actinia ahyssicola and A. gelatinosa, adapted to adhere to dead Alcyo- 

 narian stems, and to the hollowing out of the base of Corallimorphus for attachment to 

 small bodies, such as manganese nodules. 



The genus Corallimorphus is of especial value, as appearing to be the nearest ally 

 amongst Actiniaria of many simple discoid corals, and for the excessively large size of 

 one form of its thread-cells or nematocysts ; these nematocysts seeming to be the largest 

 hitherto observed in any animal. There can be little doubt that Oceanactis is a pelagic, 

 and not a deep-sea form. Pelagic animals, such as Pyrosoma, Medusce, &c, were con- 

 stantly found in the trawl, caught by it on its way up or down, and mixed up with the 

 deep-sea animals from the botom. Pelagonemertes was obtained in this way. 



DESCEIPTION OP PLATE XLV. 



Fig. 1. Nautactis purpureus : side view, magnified. Actual height of the animal 7 millims. 



Fig. 2. Enlarged view of portion of the disk of the same, to show arrangement of the colouring. 



Fig. 3. Larval Minyad from the surface-net at the Philippines. Enlarged 15 diameters. Actual height 



1*5 millim. 

 Fig. 4. Oceanactis rhododactylus. Twice natural size. 

 Fig. 5. Actinia abyssicola, attached to a Mopsia stem. Twice natural size. 

 Fig. 6. Actinia gelatinosa. The animal is shown of half the natural size. The line of continuation of 



the rod to which the Actinia was attached within its sheath is shown by dotted lines : a, spot at 



which the body doubled upon itself. 

 Fig. 7. Corallimorphus profundus. Side view, showing the attachment of the base to a small manganese 



nodule. 

 Fig. 8. The same. Direct view from above of the disk. Figs. 7 and 8 both of natural size. 

 Fig. 8a. Nematocyst of same in quiescent, and 8 6 in active condition, x 510. Actual length of 



cell - 044 millim. 

 Fig. 9. Corallimorphus rigidus. Diagram of the disk, to show the arrangement of the tentacles and 



their proportionate sizes. 



* " On the Colouring-matters of various Animals, and especially of Deep-sea forms dredged by H.M.S. ' Chal- 

 lenger.' " By H. N. Moseley. (Quart. Joura. of Microsc. Science, vol. svii. p. 1, 1877.) 



