Mr. Gwyn Jeffreys on Dredging among the Hebrides. 898 
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 Algze) disappear in 
about 200 fathoms; and the only vegetable organisms which 
descend to a greater depth, say 400 fathoms, are Diatomacez. 
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 excavata (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 (7. 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 are 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 Lovén has lately given us fuller information, which is 
published in the ‘ Transactions of Scandinavian Naturalists’ at 
their ninth meeting held in 1863+. A Brooke’s lead and a 
‘Bulldog’ machine, with several improvements, were used on this 
occasion. Depths from 6000 to 8400 feet (1000-1400 fathoms f{) 
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 Diatomaceze$ and Polythalamia, and nearly devoid 
of sand. Professor Lovén was furnished with the notes of 
* British Conchology, vol. i. Intr. pp. xlviii-l, and vol. ii. Intr. 
pp: Vill—X1. 
+ Stockholm, 1865: p. 384. 
+ 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 Diatomacez observed by Lovén had actually lived on the sea-bottom. 
They might have been pelagic and floating kinds. 
Am. & Mag. N. Hist. Ser.3, Vol. xvii. rel 
