8 THREE CRUISES OF THE " BLAKE. 



muddy or gravelly beaches, can hardly exist in the ooze of 

 the abysses. 



The habits of many of the deep-sea dwellers are still those of 

 their shallow-water congeners, and yet their conditions of exist- 

 ence are so different that we can scarcely suppose them not to 

 have equal importance. The mollusks, annelids, Crustacea, and 

 echinoderms which find shelter in the branches of the deep- 

 water gorgonians, or the cavities, of the abyssal Euplectellse, 

 cannot be subject to the attacks of so many enemies as those 

 which live in shallower waters. 



The metamorphoses of the deep-sea echinoderms, Crustacea, 

 annelids, and mollusks must to a great extent be adapted to 

 their surroundings. Embryonic pelagic stages cannot be re- 

 tained among the deep-water genera ; these either pass through 

 the so-called abbreviated metamorphosis within the egg, as in 

 some Crustacea and annelids, or after leaving the egg envelopes 

 are kept in a kind of marsupium, as in some echinoderms ; both 

 these modes of development occur in the littoral and shallow- 

 water species. Neither is it probable that the eggs of the deep- 

 sea fishes are pelagic ; they may be either too heavy to float, 

 or in some families may be attached to the bottom. 



Previous to the deep-sea explorations the collections made 

 near the hundred-fathom line, or thereabout, were considered as 

 belonging in " deep water," so that, when examining the early 

 lists published by the English, Scandinavian, and American nat- 

 uralists, we should bear in mind that they represent a fauna 

 which scarcely extends beyond the limits of the littoral region 

 as at present understood, and include only the few deep-water 

 types which find their way to the junction of the littoral and 

 continental regions. Of course the comparisons made with the 

 strictly shore inhabitants, or those of adjacent bathymetrical 

 belts, were often interesting, but had not the wide bearing of 

 the results of later explorations. 



The bathymetrical distribution of some of the more impor- 

 tant types brings out strikingly the contrast between the faunae 

 of the submarine regions thus far recognized. An examina- 

 tion of the fishes obtained by the " Challenger," the " Blake," 

 and the " Albatross," shows that twenty-six species have a ver- 



