200 Prof. W. King on Oceanic Sediments, and 
of the sarcode was carried on within its chambers, a forami- 
nifer-shell would be limited to the superficial stratum, rising 
and sinking therein, as if it were animated and it preferred 
darkness to light. Eventually, gas ceasing to be generated, 
and the chambers becoming filled with water, the shell sinks 
to the bottom. 
These suggestions, it appears to me, are fully capable of 
explaining not only the presence of foraminifer-shells in the 
greatest abundance in the superficial stratum after sunset 
(assuming that the observations made by Major Owen and 
others are conclusive on this point*), but how it is that the 
specimens taken in the tow-net are often fresh, transparent, 
and occasionally furnished with spines in a wonderful state 
of preservation t; while those obtained from the bottom are 
usually in an opaque or chalky condition. On the view that 
these organisms habitually live at the bottom, it may be 
urged that some specimens in the living state ought to be 
brought up by the dredge or sounding-apparatus. Consider- 
able doubt, however, may be entertained as to such possessing 
any vital power, considering the greatly altered conditions of 
temperature and pressure they would be subject to during the 
ascent ; and it is highly improbable that many of them would 
retain their delicate spines. As the problem does not seem to 
be difficult of solution, let us hope that it will not remain long 
in its present unsettled state. 
As regards the nature of the various substances forming 
the sea-bottoms, the general concurrence of the recorded ob- 
servations goes far to prove that generally wherever the depth 
increases beyond 2600 fathoms the foraminifer-ooze gives 
place to argillaceous deposits, one kind marked “ grey ooze ”’ 
and the other ‘ red clay”’ in the ‘ Challenger’s’ charts,—that, 
instead of a substance convertible into limestone or chalk, 
there occurs at depths approaching and exceeding 3000 fathoms 
a sediment essentially consisting of silica, red oxide of iron, 
and alumina. The two formations pass into each other by 
* The naturalists of the ‘Challenger’ are silent on this point: on the 
contrary, they mention that Pulvinulina Menardi, which largely contri- 
butes to the formation of the ooze, is very abundant at the surface, and 
still more so during the day at a depth of from 10 to 20 fathoms. 
+ Hackel has thrown out the suggestion that the spines with which 
Orbulina and Gilobigerina are crowded “ probably contribute essentially 
to enable these little animals to float below the surface of the water by 
greatly increasing their surface, and consequently their friction against 
the water, and rendering it more difficult for them to sink.” But the 
force of this suggestion is altogether weakened by the fact that Pulvinu- 
line, equally considered to be surface-swimmers, do not possess any 
spines. 
