458 THE POPULAR SCIENCE MONTHLY. 



no fewer than eight zones of life, in the course of which the number 

 and variety of forms gradually diminished ; until, beyond 300 fathoms, 

 life disappeared altogther. Hence it appeared as if descent in the sea 

 had much the same effect on life as ascent on land. Recent investiea- 

 tions appear to show that Forbes was right enough in his classification 

 of the facts of distribution in depth as they are to be observed in the 

 jdEgean ; and though, at the time he wrote, one or two observations 

 were extant which might have warned him not to generalize too ex- 

 tensively from his iEgean experience, his own dredging- work was so 

 much more extensive and systematic than that of any other naturalist, 

 that it is not wonderful he should have felt justified in building upon 

 it. Nevertheless, so far as the limit of the range of life in depth goes, 

 Forbes's conclusion has been completely negatived, and the greatest 

 depths yet attained show not even an approach to a " zero of life : " 



" During the several cruises of H. M. ships Lightning and Porcupine in the 

 years 1868, 1869, and 1870," says Dr. Wyville Thomson, " fifty-seven hauls of 

 the dredge were taken in the Atlantic at depths beyond 500 fathoms, and six- 

 teen at depths beyond 1,000 fathoms, and, in all cases, life was abundant. In 

 1869 we took two casts in depths greater than 2,000 fathoms. In both of these 

 life was abundant ; and with the deepest cast, 2,435 fathoms, off the mouth of 

 the Bay of Biscay, we took living, well-marked, and characteristic examples of 

 all the five invertebrate sub-kingdoms. And thus the question of the existence 

 of abundant animal life at the bottom of the sea has been finally settled and for 

 all depths, for there is no reason to suppose that the depth anywhere exceeds 

 between three and four thousand fathoms ; and, if there be nothing in the con- 

 ditions of a depth of 2,500 fathoms to prevent the full development of a varied 

 Fauna, it is impossible to suppose that even an additional thousand fathoms 

 would make any great difference." ' 



As Dr. Wyville Thomson's recent letter, cited above, shows, the 

 use of the trawl, at great depths, has brought to light a still greater 

 diversity of life. Fishes came up from a depth of 600 to more than 

 1,000 fathoms, all "in a peculiar condition from the expansion of the 

 air contained in their bodies. On this relief from the extreme press- 

 ure, their eyes, especially, had a singular appearance, protruding like 

 great globes from their heads." Bivalve and univalve mollusca seem 

 to be rare at the greatest depths ; but star-fishes, sea-urchins, and other 

 echinoderms, zoophytes, sponges, and protozoa, abound. 



It is obvious that the Challenger has the privilege of opening a new 

 chapter in the history of the living world. She cannot send down her 

 dredges and her trawls into these virgin depths of the great ocean 



1 " The Depths of the Sea," p. 30. Results of a similar kind, obtained by previous 

 observers, are stated at length in the sixth chapter, pp. 267-280. The dredgings carried 

 out by Count Pourtales, under the authority of Prof. Peirce, the Superintendent of the 

 United States Coast Survey, in the years 1867, 1868, and 1869, are particularly note- 

 worthy, and it is probably nof. too much to say, in the words of Prof. Agassiz, "that we 

 owe to the coast survey the first broad and comprehensive basis for an exploration of 

 the sea-bottom on a large scale, opening a new era in zoological and geological research." 



