XIV 
THE VOYAGE OE H.M.S. CHALLENGER. 
also notes of three surface-specimens in which, the shell-wall was partially double, and of 
one in which it was partially triple. In no case were the additional layers complete, and 
they were invariably so thin that they could only he described as films ; in point of fact 
they bore no resemblance to the multiple tests of bottom-specimens. This is as far as I 
can speak from my own knowledge. I have, however, before me a pencil sketch by Mr. 
George West of a portion of a double-shelled surface-specimen of which the walls are of 
measurable thickness, being each rather under xsWth inch ('017 mm.), or altogether, 
including the interspace, about yWth inch ('034 mm.); and therefore, like the single 
specimen first mentioned, as thick as many bottom shells. But under any circumstances 
such examples are very exceptional, and the great bulk of the surface Orbulince that have 
come under my notice are precisely such as I have endeavoured to describe. It is perhaps 
needless to pursue this portion of the subject further, inasmuch as the general features of 
the genus are discussed at some length at a later page. 
Taken by themselves, the facts that have been brought forward, as well as some others 
of less significance that might be adduced, tend to the inference that the Foraminifera 
which are found living in the open ocean have also the power of supporting life on the 
surface of the bottom-ooze and further that, so far as our present knowledge goes, there 
is at least one variety of Globigerina which lives only at the sea-bottom. But this 
is only one side of the story. 
It has been suggested, for example, that the presence of bottom-specimens of Globi- 
gerina pachyderms in the “ cold area ” of the Faroe Channel, notwithstanding the entire 
absence of the species from the surface-gatherings, may be explained by the supposition 
that the former are exclusively dead shells brought by the cold bottom-current from the far 
north, and that the species will eventually be found leading a pelagic existence in the Arctic 
Seas. That is, no doubt, a possible solution of the difficulty ; and if it were necessary 
to believe that all Globigerina live only at the surface, it might be regarded as sufficient ; 
happily it is one of those points which are pretty sure to be cleared up by future investigation. 
Under ordinary circumstances there is a close and very obvious relationship between 
the pelagic fauna and that of the sea-bottom immediately beneath ; and it becomes 
evident on even a slight examination that the distribution of the constituent species of 
the former, and therefore to a considerable extent of the latter also, is dependent on the 
temperature of the surface-water. 2 
1 There is an observation recorded by Dr. Carpenter in the following paragraph that appears too important to be 
left entirely unnoticed: — 
“ Of the existence of living Globigerincc in great numbers in the stratum of water immediately above the bottom, at 
from 500 to 750 fathoms depth, I am able to speak with great positiveness. It several times happened, during the Third 
Cruise of the “ Porcupine ” in 1869, that the water brought up by the water-bottle from immediately above the Globigerina- 
ooze was quite turbid ; and this turbidity was found (by filtration) to depend, not upon the suspension of amorphous 
particles diffused through the water, but upon the presence of multitudes of young Globigerina, which were retained 
upon the filter, the water passing through it quite clear.” — Proc. Roy. Soc., vol. xxiii. p. 235. 
2 See Murray, Proc. Roy. Soc. Edin., vol. x. p. 508, Note. 
