DREDGING ON THE COASTS OF SHETLAND. 71 
reality no sharp and abrupt lines in the picture, such as the inventive but 
partially instructed mind of man is apt to conceive when he frames what he 
considers a perfect system of classification. Marine animals do not seem to 
care so much whether there are five or five hundred fathoms of water over 
them, as whether they have a sufficient supply of food and the requisite 
shelter. It is extremely desirable to know more about the conditions of their 
habitability and the limits of depth within which each species can thrive or 
exist. In a geological point of view, the importance of this subject cannot be too 
highly estimated, especially as regards the last-mentioned subject of inquiry. 
At present we have no satisfactory information as to the depth of the primeval 
seas. It was at one time conjectured that the absence of colour was a test of 
depth ; but it has now been ascertained that the most brilliant and variegated 
hues are not wanting in living creatures obtained from the abysses of the 
ocean, My friend Dr. Otto Torell informs me that during his last expedition 
to the Arctic seas, which was undertaken at the instance and cost of the 
Swedish Government, he found a large and undescribed kind of coral, on which 
were three live specimens of an Actinia of a bright red colour. The coral and 
its appendages were entangled in the machine which was sunk to the bottom 
of thesea. The depth was 1480 fathoms, being more than a mile and two- 
thirds in vertical measurement. Dr. Wallich has also given, in his valuable 
work ‘The North-Atlantic Sea-bed,’ a highly interesting account of the 
capture of living and full-grown star-fishes (Ophiocoma granulata), of a dusky- 
brown colour, at a depth of 1260 fathoms. It is beyond all doubt that the 
coral, sea-anemones, and starfishes actually lived on the sea-bottom whence 
they were taken, and that they had not been accidentally transported to the 
spot by any current, much less that any of them could have been swimming 
or floating, so as to become thus entangled in the sounding-apparatus or rope 
on its passage upwards through the water. Dr, Wallich has clearly refuted 
the objection, which was at one time made to his statement, that the star- 
fishes might either have been drifted to the position in which they were 
discovered by a superficial or deep-seated current, or else that they might 
have propelled themselves to it from some distant coast-line, The habits of 
these animals, and the nature of the organisms found in their digestive cavities, 
would render the latter proposition extremely improbable, if not impossible ; 
while the direction of the only upper current which is known to flow in that 
course, and the conditions resulting from a lower current (if any such exists), 
would show that the phenomenon could not be explained in this way. In 
our own seas, and especially in that part which washes the coasts of Shetland, 
I have frequently dredged, at depths between 80 and 90 fathoms, living 
Mollusca whose shells were marked with stripes, bands, and spots of the 
most vivid colour; and these were of species which also inhabit shallow 
water on other parts of our coast, and which are often in the latter case 
colourless. Pectunculus glycymeris was here found to be variegated by rich 
streaks and zigzag blotches of reddish-brown; Yellina pusilla had bright rosy 
trays; Psammobia costulata exhibited delicate pink markings; Zrochus zizy- 
phinus had a uniform brick-red hue; and Natica marochiensis was spotted with 
purplish-brown. The animal of Marginella levis also was beautifully painted, 
and displayed its gaudy tints of green, pink, and flake-white. Other geological 
problems of equal interest may be solved by the use of the dredge; and some 
of them will be presently noticed. 
There is likewise another aspect in which these researches may be regarded 
in connexion with the British Association, The first object of the Association, 
as declared by its promoters and accepted as the basis of the institution, is 
