30 AMERICAN JOURNAL 



2 ; Rhizopoda (Foraminifera) 19 ; Polypi (Actinozoa) 7 ; Mol- 

 lusca (Polyzoa 8, Tunicata 1, Mollusca proper 10) 19 ; and Ver- 

 mes (Annelida) 5. He has also specified several Echinoderms, 

 Cirripeds, and Crustacea, as inhabiting somewhat less depths, 

 viz., from 200 to 250 fathoms. The observations of the learned 

 Norwegian zoologist confirm those of Sir James Ross and Dr. 

 Wallich, namely : — 



1st. That the temperature of the sea is uniform (89° -5 Fahr.) 

 over the whole globe, below a certain line which forms an isother- 

 mal curve, with but slight oscillations caused by changes of the 

 atmosphere. This curve has its greatest depth at the Equator, 

 but reaches the surface of the ocean in lat. 56° 62', and dips 

 again as it approaches the pole from this point. 



2d. Although the pressure of the water is enormous at great 

 depths, and in 300 fathoms is equal to about 56 atmospheres or 

 840 lbs. on the square inch,* yet the most brittle and delicate 

 animals (such as Polyzoa and Polyps) inhabiting such depths do 

 not appear to suffer the slightest injury. Their structure is por- 

 ous and permeable by liquids, or accessible to an endosmotic in- 

 fluence by which the pressure is easily resisted. 



3d. The want of light has always been considered an obstacle 

 to the existence of animal life at great depth — not so much be- 

 cause light is directly essential to animal life, as on account of 

 its indirectly contributing to its maintenance. It is generally 

 supposed that animals are dependent on vegetable life. This 

 latter, as is well known, cannot exist without light, under the in- 

 fluence of which the absorption of carbonic acid and the evolu- 

 tion of oxygen are effected. Light, however, exerts no such in- 

 fluence on animal life. Sea-weeds (the true Algae) disappear in 

 about 200 fathoms ; and the only vegetable organisms which de- 

 scend to a greater depth, say 400 fathoms, are Diatomaceje. It 

 may be observed, with respect to the action of light in producing 

 color in animals, that although intensity of light may produce a 

 corresponding intensity of color under ordinary circumstances, 

 yet the diminution or absence of light in the sea is not neces- 

 sarily followed by a diminution or absence of color in marine 

 animals. Those taken from considerable depths have frequently 

 vivid colors. The animal of Lima excavnta (a comparatively 

 gigantic species), from 300 fathoms, is of the same bright red 

 color as those of L. Loscomhii and L. Mans from shallow water. 

 It has been shown that red rays of light (^'. e. actinic contradis- 

 tinguished from luminous rays) penetrate deepest in the water. 



*The Norse skaalpund is 10 per cent, more than the English lb. avoir- 

 dupois. Sixteen Norwegian square inches are equal to seventeen English 

 square inches. 



