1432 
THE VOYAGE OF H.M.S. CHALLENGER. 
Number of 
Individuals op 
ONE Species in 
Hekp-Sea 
Trawlinc.s. 
Comparison of 
1'eep-Sba and 
Shallow-Water 
Hauls with the 
Tbawi_ 
There were over thirty specimens of the little sea-urchin, Urechinus naresianus, in the 
trawl at Station 14G in 1375 fathoms, but as a rule, in the Challenger trawlings deeper 
than 1000 fathoms, it was unusual to take more than four or five specimens of any one 
species in a single haul. Indeed, a great number of genera as well as species, in 
proportion to the number of specimens, is the marked peculiarity of these hauls in very 
deep water. In depths less than 1000 fathoms, and especially in depths less than 500 
fathoms, immense numbers of individuals, all belonging to the same species, may be 
captured in a single haul. At Station 166, in 275 fathoms, the specimens of Pandalus 
magnocuhis were so very numerous that they were served on the ward-room table. In 
555 filth oms in the Faroe Channel over four hundred specimens of Lsetmogone violacea 
were procured in a single haul. The only other known specimens of this species were 
captured by the Challenger at the very antipodes in 410 fathoms off the east coast of 
Australia. In the Faroe Channel the “Triton” also captured in a single haul of the 
trawl, from a depth of 540 fathoms, over one thousand specimens of Pycnogonids, 
chiefly belonging to one species of Nymphon. Similar instances might be mentioned in 
which large numbers of Rossella, Euplectella, and other organisms, all belonging to 
one species, were taken in single hauls in depths between 100 and 300 fathoms. 
It is interesting to compare single hauls made in the deep sea and in shallow water 
with respect to the number of different species obtained. For instance, at Station 146 in 
the Southern Ocean, at a depth of 1375 fathoms, the 200 specimens captured belonged to 
59 genera and 78 species. The trawl made use of had only a 10-feet beam. In working 
at sucli a depth it is not possible to say how long or for what distance the trawl had 
been dragged over the bottom, — two hours, and a distance of two miles, would probably 
lie an e.xcessive estimate. In depths less than 50 fathoms, on the other hand, I cannot 
find in all my experiments any record of such a variety of organisms in any single 
haul, even when using much larger trawls and dragging over much greater distances. 
The statistics of the Scottish Fishery Board’s trawlings in the North Sea, with a 25-feet 
beam in depths less than 80 fathoms, show the average catch per haul of many 
trawlings to be 7 '3 species for invertebrates and 8 ’3 species for fishes, the greatest 
number of both invertebrates and fishes recorded in any one haul being 29 species.* 
My own trawlings off the west coast of Scotland, in depths between 40 and 100 fathoms 
on muddy Ixittoms, gave usually a much greater number of species per haul than this, 
sometimes as many as 50 species, still not such a great variety of animals as was 
j>rocured in many instances by the Challenger’s small trawl in great depths. 
The great abundance of both individuals and species in deep water, and the peculiar 
adaptations among deep-sea animals to the conditions of their existence, all point to the 
' I am indebU*d to Dr Fulton of the Scottish Fishery Board for these particulars. 
