Prof. T. Fuchs on the Deep-sea Fauna. 7 



thcless it is well known that they cannot well go below 8-10 

 fathoms, and that they are never met with living below 20 



fathoms. 



In the Ked Sea a temperature of 21° C. prevails down to 

 the bottom at a depth of 600 fathoms, and consquently tropical 

 organisms might occur down to a depth of 600 fathoms. But, 

 so far as we are yet acquainted with the characters of the 

 Red Sea, this appears to be by no means the case ; and with 

 I regard to the coral-reefs and their fauna we know with cer- 



I tainty that in general they do not extend further down here 



than elsewhere, u e. 8-10 fathoms, and that living reef-corals 

 are never found below 25° C. 



There is also another fact which is equally convincing. Tn 

 the Polar seas there prevails perennially, from the surface 

 down to the greatest depths, a uniform temperature of about 

 0° C. (32° F.), which only rarely rises 1° or 2° higher, or 

 falls to about the same extent. If, now, the temperature were 

 the limiting factor in the bathymetrical distribution of organ- 

 s, we ought properly, in the Arctic and Polar seas, to 

 meet with the deep-sea fauna in the littoral region, and here 

 that contrast between the littoral and deep-sea faunas which 

 prevails in the warmer seas could by no means occur. As is 

 well known, however, none of these suppositions are correct. 

 In the littoral region of the Arctic and Polar seas we find no 

 traces of deep-sea Corals and Brachiopoda, of vitreous sponges, 

 Echinothurice, and Pour tales ice , no trace of Crinoids, Brtsingce, 

 Elasmopodia, or of that swarm of remarkable Crustacea and 

 fishes which characterize the deep-sea fauna. All these forms 

 of animals occur, indeed, in the Arctic seas, but here also 

 always only in the deep water, and not in the littoral region ; 

 and here the general contrast between the littoral and deep- 

 sea faunas is just as sharply defined, and in the same manner, 

 as in warmer seas. 



It is true, indeed, as already stated, that there are some 

 species of animals which, in warm seas, are found only in deep 

 water, but which occur in shallow water in the Arctic seas ; 

 but their number is so inconsiderable, and they are at the 

 same time so uncharacteristic, that they in no respect merit 

 the importance which has hitherto been ascribed to them. It 

 must also be noticed that very many of those so-called "arctic" 

 animals which are found at great depths in southern latitudes 

 only bear the designation - arctic " because they were first 

 known from the Arctic seas ; but that even here they by no 

 means occur in the littoral region, but are also confined to the 

 deep water as in warmer seas. Moreover there are also a 

 number of species of animals which are found in warmer 



