78 Dr. G. C. Wallich on the Process of 
aperture of the last-formed chamber, after the fashion of Gro- 
mia*, 
Of the highly important office performed by this outer layer, 
there appears to be no room for doubt. Owing to this import- 
ance, and the misconception that would inevitably arise were it 
to be regarded as made up of ectosare alone, I have thought it 
necessary to distinguish it from the rest of the soft mass by 
the name of chitosare (xiT@v, a coat). But it must be ex- 
pressly understood that this layer is not distinct in constitution 
from the rest of the sarcode, but formed out of it, and (as in the 
case of the naked Rhizopods) continually intermingling with 
the internal portion by ameebasis. It is through the agency of 
the internal surface of this layer or chitosarc that the increase in 
the thickness and strength of the shell is effected, the various 
complicated canal-systems formed, and all secondary deposits 
and the entire series of surface-markings of the Foraminifera 
produced+. 
This layer would seem to be present in all the testaceous genera 
of Rhizopods. In Gromiait has long been recognized, aud sup- 
posed to be altogether derived from a reflexion of the sarcode-mass 
issuing at the mouth of the test. In the Polycystina, as in the 
Foraminifera, it undoubtedly produces all the beautiful sculp- 
turings for which these organisms are so celebrated. The growth 
of the siliceous framework of the Acanthometrina and Dictyochide 
is almost wholly dependent on its presence; whereas in the highest 
order of Rhizopods, namely the Proteina, it is extremely proba- 
ble that it occurs also in all the testaceous genera, although, 
from the greater differentiation of the sarcode-substance gene- 
nerally, it is more delicate and less easily traceable. In this 
order I have not seen it; but there seems reason to suspect that 
in Euglypha and indeed all the Lagynidz, and also in the tes- 
taceous Ameebans (as in Difflugia and Arcella), it is not only 
reflected from the main orifice, but escapes partly through the 
minute pore or pores which are distinctly visible at the apex of 
the test in Huglypha, Cadium, Protocystis (Wall.), and Difflugia. 
In the latter genus the pore is at times produced into a hollow 
cylindrical tube of some length, as shown in my paper on Ameba, 
* For reasons which will be given im a later portion of this paper, I am 
inclined to believe that the test of Gromia may not be strictly imperforate. 
+ The presence of an outer investing film of sarcode in certain Foramini- 
fera appears to have been recognized by Dr. Carpenter and Prof. Schultze. 
In the ‘ Introduction to the Study of the Foraminifera’ (p. 128), the former 
author accounts for the exceptional structure of Dactylopora by ascribing 
its formation to this outer film, and cites Gromia as an example in which 
it is reflected back over the entire test, from the sarcode-body protruded 
through the main aperture. 
