Dr. WallicHj on the Polycystina. 
67 
But this is not all ; for I believe that between the degree of 
differentiation of the sarcode body observable in the Forami- 
nifera and Polycystina no difference of importance really ex- 
ists. In both families (as may readily be seen on inspection 
of the plates above referred to) the pseudopodia are given off 
principally with reference to the number and position of the 
apertures occurring in the shell. In both, coalescence of the 
most complete kind takes place immediately on the escape 
of the sarcode stolons through the main or secondary aper- 
tures, to such an extent as occasionally to constitute a 
delicate externally investing layer, between the inner surface 
of which and the outer aspect of the shell the process of 
mineral deposit goes on. And, lastly, we find in both 
families the same intermittent and incomplete granular cir- 
culation. Now, these families have been ranked under differ- 
ent Orders. 
In Carpenter^s system the Foraminifera are associated with 
the Gromida in the first or Reticularian order; whilst the 
Polycystina are grouped with the Actinophryna, Acanihome- 
trina, and Thalassicollma, as already shown, in his second or 
Reticularian order. On the other hand, in the system of 
MM. Claparede and Lachmann the Foraminifera are isolated 
from all the other families; and, singularly enough, whilst 
no allusion is made to any predominant tendency in this 
family of the pseudopodia to coalesce, such tendency is intro- 
duced as a distinguishing character of the Gromida. Here, 
moreover, it will be seen that the Actinophryna, regarded by 
Carpenter as affording the type of the pseudopodian character 
in the Order which includes Thalassicolla and Acanthometra, 
are separated from both of these last-mentioned families, and 
elevated to the most highly differentiated Order in which they 
occur with Amoeba. 
One illustration more, also taken from Schultze^s work, 
and I have done for the present with the discussion of pseu- 
dopodia. The figure given by Schultze of his Amoeba porrecta 
(pi. vii, fig. 18), in like manner with the figures already 
referred to, has been copied into all our leading text-books 
on the Protozoa. It is, moreover, reproduced in the ^ Intro- 
duction to the Study of the Foraminifera^^ (pi. i, fig. 18), 
with a mark of interrogation after the generic name, and 
coupled with the observation [op. cit., p. 24) that "the dif- 
ferentiation of the Rhizopod is far less complete, and the 
pseudopodia seem to be as much formed by the endosarc as 
the ectosarc, in this and other particulars presenting the 
link of transition to the shell-less Reticidaria'^ ! In other 
words, between the two extremes of tlie Ehizopod series, and 
