Dr. Wallich, on the Polycystina. 
77 
tions in form and repetition of parts, by Ehrenberg and 
Miller as regards tbe Polycystina, and by D'Orbigny and 
Scbultze as regards tbe Foraminifera. 
The evidence appears to me very inconclusive upon which 
it has been asserted that fission" and gemmation" consti- 
tute the principal mode in which the lower testaceous Rhizo- 
pods multiply. And it still remains to be determined whether 
any of the testaceous forms, whose chambers are connected 
with each other so as to admit of a complete union of the 
masses of protoplasm which they contain, ought to be re- 
garded as multiple individuals, or only as a single individual 
composed of more than a single sarcodic segment. In the 
Polycystina the individual is, I imagine, undoubtedly single. 
So it is in the case of the Protodermata, with exception of 
of the Thalassicollina. The acute perception of Huxley at 
once satisfied him of the true state of the case in T. punctata. 
He termed it a mass of cells united by jelly, like an animal 
Palmella,""^ but he clearly demonstrated that each cell of the 
series is a perfect Thalassicolla. My own observation enables 
me to show that, in this family, the increase of the number of 
individuals is not efi'ected (at least certainly not as a rule) by 
gemmation or fission, but by the evolution of the sarcoblast, 
and its subsequent extrusion from the parent structure. 
Even in the Monothalamous Foraminifera I think all the 
data we possess tend to the conckision that the new brood 
is not the result of the detachment of a molecule of sarcode 
indiscriminately from any portion of the mass of the parent 
body, but of the development of a true reproductive cor- 
puscle, namely, the sarcoblast, whether it eventually turns out 
that this corpuscule is derived from fission of the nucleus or is 
an independent formation. It would be impossible within ray 
present limits to show how far the evolution of the sarcoblast, 
in the Herpnemata [Foraminifera and Polycystina) corre- 
sponds, or fails to correspond, with its evolution in the higher 
forms — as, for example, in Amoeba. But I believe, and pos- 
sess sufficient evidence to prove, that from the sarcoblast, in 
both orders, the young animal usually originates. This is a 
very important fact, and one deserving of a much more de- 
tailed notice than can be accorded it on the present occasion. 
I allude to it in this cursory way simply to enable other ob- 
servers to verify it as opportunity offers. Now, each segment 
of sarcode in a Foraminifer can no more be said to constitute 
a separate being than each segment of an Annelid, The indi- 
viduals forming the mass of a compound Ascidian (as, for 
* " On Thalassicolla," * Annals and Magazine of Natural History,' 2nd 
ser., vol. viii, p. 434. 
