383 
of Edinburgh, Session 1881-82. 
of division, &c., to which the names of P. racliolariarum, P. 
siplionophorum , P. aciiniarum , and P. medusarum , according to 
their habitat, may conveniently he applied. 
It now remains to inquire what is the mode of life and what the 
function of such organisms. I accordingly exposed a quantity of 
Radiolarians, chiefly Collozoum inerme , to sunshine, and was 
delighted to find them soon studded with tiny gas bubbles. 
Although 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, hut was partly taken up when pyrogallic acid was 
added. Thus little or no carbonic acid was present; hut 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 21 to 24 per cent, of oxygen, that subsequently 
squeezed out of 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 Antliea cereus , which yielded great 
quantities of gas, containing on an average from 32 to 38 per cent, 
of oxygen.* 
At first sight it might seem impossible to reconcile this copious 
evolution of oxygen with the completely negative results obtained 
from the same animal by so careful an experimenter as Kruken- 
berg, yet the difficulty is more apparent than real. I was at 
length able to obtain, through the kindness of Dr. Andres, 
a large and beautiful specimen of Antliea cereus, var. smarag- 
dina , which has its tentacles tipped with purple, and of a 
far more beautiful green than that with which I had before 
been operating, the dingy brownish olive var. plumosa. The 
former owes its colour to a green pigment diffused chiefly 
through the ectoderm, but has comparatively few algae in its 
endoderm, while in the latter the ectodermic pigment is present in 
much reduced quantity, but the endoderm cells are crowded with 
algae. The specimen just referred to, and also one of plumosa, were 
placed in similar vessels side by side, and exposed to full sunshine ; 
by afternoon the specimen of plumosa had evolved gas enough for 
* The amount of gas taken for analysis varied between 2 and 5 c. c. , and 
averaged about 3 ‘5 c.c. 
