, for which the
name of _P. radiolarum, P. siphonophorum, P. actiniarum_, and _P.
medusarum_, according to their habitat, may be conveniently adopted.
It now remains to inquire what is their mode of life, and what their
function.
I next exposed a quantity of Radiolarians (chiefly _Collozoum_) to
sunshine, and was delighted to find them soon studded with tiny
gas-bubbles. Though it was not possible to obtain enough for a
quantitative analysis, I was able to satisfy myself that the gas was not
absorbed by caustic potash, but was partly taken up by pyrogallic acid,
that is to say, that little or no carbonic acid was present, but that a
fair amount of oxygen was present, diluted of course by nitrogen.
The exposure of a shoal of the beautiful blue pelagic Siphonophore,
_Velella_, for a few hours, enabled me to collect a large quantity of
gas, which yielded from 24 to 25 per cent. of oxygen, that subsequently
squeezed out from the interior of the chambered cartilaginous float,
giving only 5 per cent. But the most startling result was obtained
by the exposure of the common _Anthea cereus_, which yielded great
quantities of gas containing on an average from 32 to 38 per cent.
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