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



possessing a uniform temperature of from 12° to 13° C. (53°'6 to 



55° # 4 F.). Nevertheless it possesses a perfectly well-marked 



and tolerably rich deep-sea fauna ; for besides the multifarious 

 deep-sea corals, Brachiopotla, and various deep-sea Mollusca 

 which were previously known, a whole series of true deep-sea 

 animals not previously known from this sea were discovered 

 in the course of last summer (1881) by the dredging-expe- 

 dition of the French ship i Travailleur ' *, such as several vitre- 

 ous sponges (Tetilla, Iloltenia), deep-sea starfishes (Archaster 

 bifronsy Aster ias Richardi), the genus Brisinga, and numerous 

 deep-sea Crustacea (Dorht/nchus 9 GergoUj Ebalia, Ethusa, 

 Muni da, Lophogaster, Galathodes) , several of which are blind. 



On the Euplectella- grounds which occur at a deptli of 100 

 fathoms near the Philippines, the temperature, according to 

 Semper, is 15° C. (59° F.), and off the island of Cebu, ac- 

 cording to Moseley, even 21° C. (69°-8 F.)f. A fauna of 

 precisely similar character and exactly similar composition 

 occurs, however, as already mentioned, in other places at a 

 temperature of 0° C, and still lower. 



If we once more glance over what has just been stated, 

 taking it in connexion, it becomes so clear that the occurrence 

 of the deep-sea fauna is in no way connected with the tempe- 

 rature of the water, that it would be superfluous to point this 

 out again expressly. But if it is not the temperature that 

 causes the appearance of the deep-sea fauna, what is the con- 

 dition governing it ? 



The chemical characters of the water, the amount of ab- 

 sorbed air contained in it, or the movement of the water have 

 been suggested ; but not one of tliese conditions seems to agree 

 with the existing circumstances. The chemical characters of 

 sea-water show no essential differences from the surface to the 

 bottom. The amount and relative composition of the absorbed 

 air certainly present some alteration with increasing depth ; 

 but this alteration is scarcely of any consequence at a depth 

 of 50 fathoms, and could only exert a perceptible influence 

 much lower down. 



As regards the movement of the water, if we only take 

 into consideration the wave-movements produced by storms, 

 the circumstances appear at the first glance rather more 



* Milne-Edwards, " Compte rendu sommaire d'ime exploration zoolo- 

 gique faite dans la Mediterranee a bord du navire de Tetat 4 Le Travail- 

 leur ' * (Coniptes Rendus, 1881, p. $70) ; translated in Ann. & Mag. Nat. 

 Hist. ser. 5, vol. ix. p. 87. 



t Besides Euplectella and other vitreous sponges, the following Eehino- 

 dermata also occur off Cebu at the above depth : — Salenia hastigera, 

 Aspidodiadt?na toutum, Micropyga tubtrctdatum, Atthenosoma pellucidum\ 



