ON THE RADIOLARIA AS AN ORDER OF THE PROTOZOA. 369 
the capsular wall into the peripheral stratum of sarcode. In 
Sphcerozoum and other members of the Thalassicollidce, the 
transit of these bodies from within the capsular chamber to 
the space between it and the perforated siliceous shell appears 
almost certain, although I am not aware that the occurrence of 
a sarcoblast actually in course of transit through the capsule 
has as yet been noticed. But although it would obviously be 
premature to deny that any permanent apertures exist in it 
simply because they defy our vision, I am strongly inclined 
to suspect that they do emerge, and that the orifices are im- 
mediately sealed up again, since no mere osmotic action could 
possibly account for the phenomena. But until the existence of 
permanent apertures, or the actual transit of the sarcoblasts, 
despite the absence of such, shall have been seen, the whole 
question must, of course, remain an open one. 
But to return to the arguments based upon the presence of 
the capsule. It is admitted by the supporters of u multiple cell- 
formation amongst the Radiolaria ” (I presume only amongst 
the composite forms), that reproduction may take place : firstly, 
u by spontaneous fission or giving off a single or a few capsules, 
these modes of increase having, however, not been actually ob- 
served, though it is certain that single capsules (however derived, 
whether from spores or from segmentation) do exisEseparately. 
The colonies may also be increased by juxtaposition, and the 
mass of an existing colony by the rapid fission of its com- 
ponent capsules, the process taking place centrifugally in the 
shelled and irregularly in the shelless (sic) forms. Secondly, 
with regard to the capsules themselves, it is certain that they 
may increase by spontaneous fission into two, three, or more 
secondary capsules, and that this process may repeat itself 
indefinitely. Thirdly, with regard to reproduction by spores,* 
it is certain that such a process occurs in Acanthometra , 
Thalassicolla , Sphcerozoum , Collosphcera , and Collozoum, and 
most probably in all the Radiolarians. The spores are formed 
by the breaking up of the contents of the central capsule into 
small particles, which become directly transformed into spores, 
each spore containing a nucleus and fat-g ranules, and also a 
crystalline body, when such bodies are found within the capsules 
in which such spores arise. Each spore is provided with a 
flagellum , and it is doubtful whether more than one flagellum 
ever exists to one spore.” (Memoir, p. 167.) 
* It will "be seen that here, as elsewhere, in Mr. Mivart’s observations, the 
terms “ zoospores ” and 11 spores ” are both employed in describing the repro- 
ductive process in the Radiolaria. This must necessarily lead to great con- 
fusion, even were it possible, which it is not, to admit spore-formation in 
a single family of the true Rhizopods. 
NEW SERIES, VOL. II. — NO. VIII. B B 
