THE VOYAGE OE H.M.S. CHALLENGER. 
xii 
only were the Foraminifera, whether judged by individual specimens or by an average, 
very definitely smaller than those of the bottom-deposits, but the shells were unmis- 
takably thinner and more delicate. The same has not been the case in many of the 
mountings I have since examined ; and the result of a fresh and somewhat extensive 
series of comparative measurements has convinced me that (with some reservation as to 
Orbulina) there is no sufficient difference between the surface- and bottom-shells, either 
as to size or substance, to serve as the foundation of a general argument. 
It appears at first sight a very simple matter to determine whether organisms dredged 
from the sea-bottom have in reality lived there ; but this is far from being the case with 
respect to the microzoa. The bed of the ocean is composed of deposits of unknown 
thickness, consisting in many places chiefly of Foraminiferal remains which have been 
accumulating for countless ages. Under any circumstances it is only in the thin superficial 
film that living specimens are to be found, and even there they are mixed with a large pro- 
portion of dead and empty shells. The masses of ooze brought up by means of a heavy 
dredge or trawl, possibly representing a layer of the sea-bottom several inches thick, are mani- 
festly useless for investigations of this sort unless examined immediately on arriving at the 
surface, before the different portions have become intermixed ; indeed it would be almost 
as reasonable to expect to find sarcode animals in a Tertiary deposit as in the bulk of the 
material so obtained. This remark does not apply in the same degree to the samples 
obtained by the smaller sounding appliances. The old method of taking soundings with 
the greased lead, though of little utility for the wider purposes of zoological research, was 
perhaps better adapted for securing a knowledge of the thin superficial layer ; and it is 
quite possible that some of the discrepancies in the accounts given by different observers 
may be due to the different methods by which their material was collected. 
Where a tow-net can be attached to the dredge or trawl, so as to receive amongst 
other things the organisms thrown up by the rough disturbance of the surface of 
the bottom-mud, the contents are often of somewhat different character to those of 
the dredge itself. Not unfrequently a portion of the Foraminiferal shells collected by 
this means are filled with sarcode ; and from such material, after treatment with 
acid, I have obtained the sarcode-bodies of a number of pelagic species ; amongst 
them, in addition to some of the varieties of Globigerina, easily recognised specimens of 
Sphoeroidina dehiscens and Pulvinulina menardii. It is possible, of course, that these 
may have been pelagic specimens collected by the net during its passage through the 
water, but there was nothing in their appearance to suggest that their origin was different 
from that of the other Foraminifera in the same gatherings ; and they have at times pre- 
sented themselves in numbers far too large, as it appears to me, to be satisfactorily 
accounted for on that supposition. The sarcode, in all cases, was yellowish-brown and 
granular, precisely resembling that of in-shore Rhizopods that have in like manner 
been kept some time in alcohol before being decalcified. The soft, jelly-like lobes 
