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the characters of the three orders into which he proposes to distribute the
various families are concisely stated as follows :—
“ I. E e t i c u l a b i a . The body composed of homogeneous granular protoplasm,
without any distinction into ectosaro and endosarc; neither nucleus nor contractile
vesicle; pseudopodia composed of the same substance as the body,
extending and multiplying themselves by minute ramification, and inosculating
completely wherever they come into contact ; a continual circulation of granular
particles throughout the viscid substance of the body and its extensions. This
Order consists of the Foraminifera and the Gromida.
II. EADI0L.4EIA. Incipient differentiation of the protoplasmic substance into
ectosaro and endosarc, the former semifluid and granular, the latter more
tenacious and pellucid ; a nucleus and contractile vesicle ; pseudopodia rod-like,
usually tapering from base to point, composed of the same substance as the
ectosarc, exhibiting little disposition either to ramify or to coalesce, having
a more or less regular radiating arrangement, and not showing any constant
circulation of granules in their substance, although a movement of particles
adherent to their exterior is often to be distinguished. The type of this
Order is Actinophrys, constituting, with its immediate allies, the family
Actinophryna ; but tbe Order also includes the Acanthemetrina, Polycystina, and
Thalassicollina, by the last of which this group is connected with the Sponges.
“ III. L o b o s a . More complete differentiation of the protoplasmic substance into
endosarc and ectosarc, the former being a slightly viscous granular liquid, and
the latter approaching the tenacity of a membrane ; a nucleus and contractile
vesicle; pseqdopodia few and large, being in reality lobose extensions of the
body which neither ramify nor coalesce, having well-defined margins, and not
exhibiting any movement of granules on their surface, the circulation in their
interior being entirely dependent on the changes of form which the body undergoes
as a whole. This Order is composed of but a single famUy, the Amoelina,
and it is the one which presents the nearest approximation to the Classes Infusoria
and Greyarinida.’'
I t will be seen that whilst these definitions are almost wholly based on the
degree of “ differentiation ” exhibited by the general mass of the sarcodic
substance, the names of the Orders point exclusively to the characters of the
pseudopodia. For, whether we regard the degree of consolidation of the
superficial protoplasmic layer of the organism—the capability or otherwise of the
pseudopodial processes to maintain a separate individuality so long as they
remain projected beyond the main mass of the body—the apparent character of
the minute granular circulation, either as occurring within the general cavity of
the organism or extending into the pseudopodia—or the presence or absence of
a nucleus and contractile vesicle,—we perceive that the whole of these characters
have a mutual dependence one on the other, and are exponents of the gradual
advance from that simplest phase of animal being in which the structure is
distinguishable from an inanimate jelly only by the cyclosis of granules and the
projection of pseudopodia, to the highest phase of Ehizopodal development, in
which the characters merge into those of the Spongidæ on the one hand and
the ciliated Infusoria on the other.
Being fully convinced that the principle of classification so admirablypropounded
by Dr. Carpenter is the only one on which a natural distribution of the Ehizo-
podal Orders can be established, it is with great diffidence that I now venture to
offer such a modification of his arrangement as I conceive to be demanded, not
by a conflict of opinion regarding the value of certain characters, but the
presence or absence of those characters in some of the families said to exhibit
them. At the same time it is a satisfaction to feel that my views diverge from
his, for the most part, only in those cases in which his judgment has been based on
the descriptions of other observers, and not on personal examination of the liring
structures.
The principal source of confusion has arisen, I conceive, from Professor
Miiller’s statements with reference to the natui-e and characters of the pseudopodial
processes in the Folycystina and Acanfhometnna—statements which clearly
tend to indicate a similarity, if not an identity, in the pseudopodia of these two
families, although I cannot admit that they warrant the conclusion that any
dissimilarity existed, in Professor Miiller’s opinion, between those of the Polycystina
and Foraminifera. In drawing attention to the additions to our previous
knowledge of the Rhizopods, supplied iu Professor Miiller’s treatise ‘ fiber die
Thalassicollen, Polycystinen und Acanthometreu des Mittelmeeres,’ Dr. Carpenter
speaks of the author as haring failed to appreciate the essential relationship
between the Acanfhomctrina and Actinophryna, “ an Acanthometra being nothing
else than an Actinophrys furnished with a siliceous skeleton.” As described by