thety Relation to Geological Formations. 199 
sinking in it at will; but there is nothing recorded to support 
the idea that they are alive, except their occurring in the greatest 
numbers on the surface after sunset ; from which it is inferred 
that they avoid the light. The presumed fact is certainly sin- 
gular if the creatures are dead, though it may not be beyond 
a physical explanation. But if they are living, it is equally 
singular that no manifestations of vital functions have been 
observed, as far as I can ascertain, in any captured specimens, 
by those who have had the opportunity of examining them. 
Prof. Wyville Thomson and assistant Mr. Murray (who has 
been paying the closest attention to the floating F oraminifera) 
would scarcely be unmindful of this matter; yet it is note- 
worthy that they “never have been able to detect in any of 
the large number of Globigerine which have been examined ” 
by them “the least trace of pseudopodia, or any extension 
in any form of the sarcode beyond the shell.” Moreover 
the chambers are often almost empty, even in the freshest- 
looking specimens ; or they contain sarcode apparently im 
no other than the  unsatisfactor y condition it presented to 
Bailey, Ehrenberg, Wallich, and others. So far, then, I see 
no reason to change the opinion which is expressed in my 
Notices of 1862. 
In order to explain all the circumstances under which the 
ooze-forming foraminifers occur, [ am induced to make the 
following suggestions in accordance with the assumption that 
they live atthe bottom. Assoon asa Globigerine or an Orbu- 
line dies, the decomposition of the sarcode generates within 
the chambers sufficient carbonic-acid gas to cause it to rise to the 
surface. Here, the sarcode being still in process of decomposi- 
tion, gas continues to be discharged from the chambers alter- 
nately with the intromission of water: these actions give rise 
to variations in the specific gravity and, as a consequence, to 
opposite vertical movements of the shell. It is conceivable, 
all other conditions being favourable, that occasionally, after 
the superficial stratum of the ocean has got warmed by the 
noon-day sun, the elevated temperature, and the consequent 
acceleration of the decomposition of the sarcode, would largely 
increase the generation of gas, thereby causing the shell to 
rise to or near the surface towards or after snnset: during the 
night, on the gas escaping and its replacement by water, the 
shell would descend again *. Thus, as long as decomposition 
* It is stated by Lewy that the amount of oxygen in sea-water is 
somewhat greater during the day than it is at night, the reverse being 
the case as Tegards carbonic acid (Bischof, vol. i. p. 115). May not this 
difference have something to do with the rising of the shells during the 
night ? 
14* 
