Mr. Gwyu JefFieys on Dredying among the Hebrides. 393 



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

 to the existence of animal life at great depths — not so much 

 because 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 influ- 

 ence of which the absorption of carbonic acid and the evolution 

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

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

 about 200 fathoms ; and the only vegetable organisms which 

 descend to a greater depth, say 400 fathoms, are Diatomacese. 

 It may be observed, with respect to the action of light in pro- 

 ducing colour in animals, that although intensity of light may 

 produce a corresponding intensity of colour under ordinary cir- 

 cumstances, yet the diminution or absence of light in the sea is 

 not necessarily followed by a diminution or absence of colour in 

 marine animals. Those taken from considerable depths have 

 frequently vivid colours. The animal of Lima eoccavata (a com- 

 paratively gigantic species), from 300 fathoms, is of the same 

 bright red colour as those of L. Loscombii and L. hians from 

 shallow water. It has been shown that red rays of light {i. e. 

 actinic contradistinguished from luminous rays) penetrate deepest 

 in the water. I will not here repeat what I have already pub- 

 lished* on this interesting subject ; but I may add that all the 

 animals recorded as living at great depths ai'C zoophagous, none 

 of them phytophagous. The deep-sea dredgings of the Swedish 

 Expedition to Spitzbergen in 1861 yielded some valuable results. 

 Adjunct Professor Thorell and Professor Keferstein communicated 

 some short and imperfect notices to the northern journals ; but 

 Professor Loven has lately given us fuller information, which is 

 published in the ' Transactions of Scandinavian Naturalists ' at 

 their ninth meeting held In 1863t- A Brooke's lead and a 

 'Bulldog' machine, with several improvements, were used on this 

 occasion. Depths from 6000 to 8100 feet (1000-1400 fathoms %) 

 were thus explored. The sea-bottom at these depths was covered 

 with a fine greasy-feeling material of a yellow-brownish or grey 

 colour, rich in Diatomacese§ and Polythalamia, and nearly devoid 

 of sand. Professor Loven was furnished with the notes of 



* British Conchology, vol. i. Intr. pp. xlviii-1, and vol. ii. Intr. 

 pp. viii-xi. 



t Stockholm, 1865 : p. 384. 



X The Swedish foot makes only 0'974 English foot. The Scandinavian 

 fathom is 6 feet. 



§ This does not quite agree with the accounts of Wallich and Sars, which 

 give 400 fathoms as the limit of vegetable life ; but it does not appear that 

 the Diatomaceae observed by Loven had actually lived on the sea-bottom. 

 They might have been pelagic and floating kinds. 



Ann. ^ Mag. N. Hist. Ser. 3. Fo/.xviii. 27 



