546 



NATURE 



{April '8, 1880 



food. In the higher latitudes it approaches shallow water. 

 In the Straits of Magellan we dredged blind Crustacea 

 and other elements of the deep-sea fauna in 120 fathoms ; 

 but even in the tropics the deep-sea fauna is met with at 

 comparatively small depths. Off St. Thomas in the 

 Danish West Indies, for example, deep-sea animals are 

 extremely abundant at 450 fathoms. 



From the upper limit of range the deep-sea fauna, 

 speaking generally, extends downwards continuously, 

 without break or defined limit of range of species or 

 genera. We had not in the Challenger time to make 

 series of dredgings to determine the upper limit of the 

 deep-sea fauna. It may lie in the places cited much 

 nearer to the surface than stated. At Cebu, in the 

 Philippines, far within the tropics, vitreous sponges occur 

 in abundance at 95 fathoms, and the deep-sea fauna may 

 almost be said there to reach that upper limit, although 

 the temperature at that depth is as high as 70° F. Mr. 

 Agassiz,' who has so thoroughly explored the deep-sea 

 off the east coast of North America and the West 

 Indies, concludes in his latest report that the range of the 

 deep-sea fauna should be carried as high as 300 or 350 

 fathoms. He terms the fauna extending from the shore 

 to 150 fathoms the littoral fauna, whilst from the 100- 

 fathom line to the 400-fathom line extend species which 



are neither littoral nor have the wide geographical distri- 

 bution belonging to forms found below that depth. We 

 might term the inhabitants of this interval the intermediate 

 fauna. Dr. Giinther tells me that he has arrived at 

 similar conclusions from his examination of the deep-sea 

 fish collected by the Challenger expedition. Below 350 

 fathoms no zones of depth are to be made "out in their 

 distribution. 



The geological bearings of these facts are all-important. 

 We shall never be able to tell from the fossil contents of 

 strata whether they were deposited at 400 or 2,500 

 fathoms. Even more, since some species and very many 

 genera range at present from the shore to vast depths, 

 many forms now restricted to deep water may formerly 

 have lived in less depths, and most probably did so. 

 Moreover as the present deep-sea fauna varies so much 

 in upward range in different places and climates, so also 

 probably did it vary in geological times. We can therefore 

 not even form conclusions of any value from these 

 grounds as to the depths at which a deposit was formed, 

 from 400 fathoms upwards, until the region of reef-coral 

 and plant-life is reached. We must rely on other 

 evidence. 



The question would not be one of much importance if, 

 as Prof. Geikie concludes, all the geological deposits with 



Fig. 7. — Odontocyathus coronatus (Moseley). 

 Magnified to twice the natural size. 



Fig. i.—Stepha 



Cnce and a half the natural 



which we have to deal are shown, by containing ripple- range. I say appear, because we have dredged some few- 

 marks and otherwise, to have been formed in shallow as yet only from one locality, but so little deep-sea 

 ■water, 9 but many geologists are, I believe, opposed to his dredging has been done that probably these will be found 

 views in this matter. elsewhere in the future. 



A most important feature of the deep-sea fauna is that No better instance of the world-wide range of deep-sea 

 it is world-wide in its distribution. I have already forms can be cited than the fact that Portuguese fisher- 

 referred to a species of coral, Bathyactis symmetrica, men fishing for deep-sea sharks in 450 fathoms off the 

 which ranges all over the world. Fig. 9 represents coast of Portugal bring up the Glass-rope Sponge entangled 



another coral, Cryptolielia pudica, which is a hydroid 

 allied to the jelly-fishes which float on the sea-surface, 

 and not to sea-anemonies like the other corals I have 

 shown. This is the common skeleton of a highly complex 

 colony. Each of the small swellings on the branches 

 contains a group of animals. In the centre of each group is 

 lodged an animal with a mouth and stomach, and all round 

 were others without mouths. The latter catch the food 

 and give it to the central animal, which digests it and 

 nourishes them and the whole coral tree by means of a 

 complex system of canals. Other animals perform solely 

 the function of rearing the young. The fully-developed 

 larvae are worm-like, and when ready escape and swim 

 away to found each a new colony. For corals, like us, 

 travel in their youth and see the world, and become 

 stationary like us only in later life. Each group of 

 animals is covered by a protective lid, hence the name of 

 the coral, Cryptohelia. It occurs all over the world in 

 from 350 to 1,500 fathoms. 

 Some few deep-sea forms appear to have a restricted 



1 Bull. Mus. Comp. 

 1 Proc. R. Gsog. So. 



»!., vol- v. Xo. 14, p. 294. 

 1879, P- 4*6- 



on their lines, and that Japanese fishermen fishing off 

 Inosima in more than 300 fathoms catch sometimes a 

 shark of the same genus as that caught by the Portuguese, 

 and bring up at the same time an almost identical sponge. 

 The sponge reached England first from Japan. 



There is absolutely nothing to restrict the geographical 

 range of animals in the deep sea. Dr. Wallich, the 

 pioneer of deep-sea research, eighteen years ago recog- 

 nised the deep homothermal sea " As the great highway 

 for animal migration, extending from pole to pole." Below 

 500 fathoms it is everywhere dark and cold, and there are 

 no ridges that rise on the ocean bottom to within 500 

 fathoms of the surface, so as to bar the migration of 

 animals in the course of generations from one ocean to 

 another, or all over the bottom of any one of the oceans. 

 The apparently shallow barriers seen in the map of 

 Atlantic and Pacific have over 1,000 fathoms of water 

 upon them. . 



Were there any variations in the conditions of life such 

 as to restrict certain animals to very great depths, as moun- 

 tain plants are restricted to certain heights on land, then 

 we might expect to find a peculiar fauna in the deep 



