April*, i88cf] 



NATURE 



545 



may exist in great depths, but it is as well to note that we 

 have not as yet been able to detect them, possibly from 

 want of adequate means and of proper search. 



Many genera of animals, and even some species have a 

 vast range of depth in the sea. Some of the animals 

 common on our sea-shores are represented in very great 

 depths by very closely allied species. As examples may 

 be cited two sea anemones from deep water. The close 

 resemblance of these to forms common in our aquariums 

 will be recognised at once. 



The one, Actinia abyssicola (Fig. 4), from 1,350 fathoms, 

 belongs to the same genus as the commonest anemony 

 exposed on the rocks all round our coast at low tide. In 

 the deep sea, in the lack of rocks for it to spread its disc 

 out flat upon, it is obliged, as in the specimen figured, to 

 cling round the dead stem of an Alcyonarian coral, or to 

 clasp some similar support. The other anemony (Fig. 5) 

 belongs to the genus Edwardsia, also found on our 

 coasts, and nearly resembles the English species, though 

 it comes from 600 fathoms. It has a long cylindrical 

 body, and covers its skin with a coating of small shells 

 gathered from the bottom mud. 



A curious sea-anemony of the genus Cerianthus, may 

 also serve as an illustration. This anemony uses its thread- 

 cells, which other anemonies and jelly-fishes use, as 

 bathers know, to sting with, to build itself a house. It 

 produces the cells, which are extremely large, in great 

 quantity, felts the threads together, and thus constructs a 

 tube in which it lives, burying the tube in the mud, and 

 expanding itself at the mouth ready to dart down into 

 safety when alarmed. The tube is about 4i inches in actual 

 length, and is covered with small foraminiferous shells 

 from the bottom, woven into it. A closely-allied species 

 lives in shallow water in the Mediterranean, and I found 

 abundance of a huge species with the tube four times as 

 long expanding its tentacles in a depth of only a foot of 

 water at low tide in the full glare of a tropical sun at the 

 Philippine Islands in water which felt quite hot to my feet. 

 Yet this deep sea form, which differs from the others in 

 little except its size, was dredged from 2,750 fathoms, 

 and inhabits a region absolutely devoid of sunlight, and 

 with a temperature always close on freezing point. 



The simple coral, Bathyactis symmetrica, of which the 

 accompanying figure (Fig. 6) represents a large specimen, 

 magnified to three times the natural size, ranges through 

 all depths from 30 fathoms to 2,900 fathoms, or three 

 miles and a quarter, almost the greatest depth from which 

 living animals have been obtained. The coral has a world- 

 wide range, occurring in all parts of the Atlantic and Pacific 

 and in the Indian Ocean. It varies very much in size, 

 some specimens being extremely minute, but I have been 

 unable to discover any relation between the size and the 

 different conditions under which the various specimens 

 lived. The size does not depend on depth, temperature, 

 or the quality of the bottom, as far as I can make out. 



When I speak of a coral I shall refer only to the skeleton 

 of the animal. The figure above represents the hard 

 skeleton of an animal like a sea-anemony. The soft 

 tissues have been entirely removed. 



In the cases of all groups of invertebrate animals, 

 annelids, mollusca, Crustacea, we find numerous similar 

 instances of the wide range of modern shore genera, and 

 even species into very great depths. For example, as 

 Mr. Davidson shows, the Brachiopod Tacbratula vitrca 

 ranges from 5 to 1,456 fathoms, whilst the genus Wald- 

 heimia ranges from shore to 2,160 fathoms, and Discina 

 from 50 to 2,425 fathoms. As Mr. P. H. Carpenter has 

 shown, the genus Antedon of our coasts ranges down to 

 2,900 fathoms. Amongst the Ophiuridae, as appears from 

 Prof. Lyman's report, the genus Amphiura ranges from 2 to 

 2,650 fathoms. Prof. Ehlers long ago showed that deep-sea 

 annelids and Gephyreans belong mostly to shallow-water 

 genera. Myriochele occurs in 2,900 fathoms, Priapulus in 

 2,750 fathoms, Balanoglossus in 2,500 fathoms, and Dr. 



Mcintosh has given me similar instances, and informs me 

 that the common shallow-water annelid, Lumbriconereis 

 fragilis, ranges down to 1,780 fathoms. From Mr. Boog 

 Watson's account of the mollusca of the Challenger 

 Expedition it appears that the common shore genus 

 Dentalium ranges down to 2,600 fathoms. Amongst 

 Crustacea Peneid and Caridid shrimps extend to all 

 depths, whilst the barnacle Scalpellum ranges down to 

 2,850 fathoms. 



Although many forms have this wide range, there are 

 certain well-marked deep-sea forms which are not met 

 with in shallow water unless in Polar regions. 



The accompanying figure (Fig. 7) represents a beautiful 

 simple coral, Odontocyathtis coronatus, from 390 fathoms 

 off St. Thomas, in the West Indies, immediate allies of 



-Bathyactis symmetrica, 'three times the natural 

 from above and edgewise. 



Viewed 



which have not been found in shallow water. The coral 

 is remarkable for having a wide flat base with tooth-like 

 spokes all round its edge, no doubt a contrivance for 

 keeping it upright as it rests on the mud at the sea bottom. 

 The genus of corals, Stephanotrochus, may also be cited 

 as confined at present, as far as known, to deep water. 

 Four species of the genus were dredged by the Challenger 

 in from 410 to 1,000 fathoms. All but one of them, which 

 was obtained off New South Wales, were dredged in the 

 Atlantic. The species here figured (Fig. 8) Stephano- 

 trochus diadema was from 1,000 fathoms off the Azores. 



There being scarcely any difference in the conditions 

 of life from a depth of 500 fathoms downwards, the deep- 

 sea fauna exhibits no zones of distribution in depth. Its 

 upward limit rises in some parts of the world higher 

 towards the coast line, in others lies lower, according to 

 the varying conditions of light temperature-currents and 



