Miiller, it would certainly seem to be nothing else; but I hope to be able to
prove as I proceed, not only that the Acanthometrina do not possess radiate
pseudopodia analogous to those of Actimrphrys, but that Acanthometra is as far
removed beyond Actinophrys, in the degree of development attained by the
ectosarc*, as Actinophrys is beyond Pamphagns or lAeierhihnia, whilst the
Polycystina, which are ranged with the Acanthometrina in Professor Miiller’s
system, do not exhibit any advance in the degree of differentiation of the protoplasmic
substance beyond that observable amongst the Foraminifera. Hence it
would appear that the separation of Actinophrys and Amceha, in Dr. Carpenter’s
system, is due rather to an assumed hut unreal affinity between Actinophrys,
Acanthometra, and the Polycystina than to any valid distinction between the
characters of the two first-named genera; for it must be admitted that the disinclination
of the pseudopodia to coalesce, and the presence of a nucleus and
contractile vesicle (the last of which organs is never to be met with in the Polycystina,
the Acanthometrina, or the Thalasdcollidce) are characters of far higher
significance than the apparent absence of granular circulation in Actinophrys,
which is seen in Amoeba, and the mere difference in size, shape, and persistence
of each pseudopodial extension. I say, apparent absence of granular circulation,
because it is difficult to conceive that in two organisms varying but little, if at
all, in the average consohdation of their ectosarc, and both possessing a nucleus
and contractile vesicle (the last of which organs Dr. Carpenterf considers as
“ superseding the necessity of the general protoplasmic circulation such a
difference should exist—or, if it exists, that it should be deemed of distinctive
value.
Had the close analogy between Actinophrys and Acanthometra really subsisted,
it is hardly possible that Professor Müller could have failed to detect it notwithstanding
the fact that his reliance on the characters furnished by the hard parts
would naturally have led him to regard these two families as distinct. But he
leaves no room for doubt as to his views concerning the pseudopodia of the
Ehizopods under notice; for he distinctly states that, having had an opportunity
* The very appropriate terms ectosarc and endosarc were originally applied by Dr. T. Strethill
Wright to the external condensed layer and the internal viscid mass of the sarcode of the Ehizopods.
t “ On the Systematic Arrangement of the Ehizopoda,” by William Carpenter, M.D., F.E.S.,
‘ Natural History Eeview,’ No. 4, Oct. 1861, p. 462.