28 
Address of the President. 
ficial portion of the sarcode having decidedly more consistence 
than the interior ; and the pseudopodia being much less freely 
extended. Still, however, the consistence of this external 
layer is not such as to present any obstacle to the reception 
of alimentary particles into the interior of the sarcode-body 
through any portion of its surface, or to interfere with the 
rejection of indigestible particles, — the temporary orifice, in 
either case, being at once closed by the coalescence of its 
edges ; so that there is obviously no definite limitary mem- 
brane, notwithstanding that the liquidity of a large part of the 
interior substance allows a free movement of granular particles 
in every direction, as I observed many years ago. Thus, the 
Amceha seems to me to represent that condition of the vege- 
table cell, in which the primordial utricle is distinguishable 
as the external more condensed layer of the protoplasmic 
mass, but does not possess the distinctness of a proper mem- 
brane. A more advanced stage is seen in the curious Gre- 
garina^ which must be regarded as corresponding with the 
Protozoa in the simplicity of its organization, whilst it resem- 
bles the Entozoa in the peculiarity of its habitat. For here, 
the distinction between the cell-wall and the cell-contents is 
decidedly marked ; the former becoming more consistent, and 
the latter more liquid. The body undergoes great changes 
of form, but no pseudopodial extensions are sent forth ; and 
the nutrient materials being imbibed in a liquid state by the 
whole surface, neither are solid particles introduced by an 
oral orifice extemporised in the superficial layer, nor are 
rejectamenta extruded through a like extemporised anus. 
Passing-on to the Infusoria, we find much reason to regard 
these simpler forms (at any rate) in the light of cells modified 
for an independent existence ; and their essential difference 
from Actinophrys and Amceha seems to lie in this, that the 
external layer of the sarcode is condensed into a more definite 
limitary membrane, — a change which involves other altera- 
tions. For, in the first place, the body can undergo compara- 
tively little change of form ; and no pseudopodia can be sent 
forth. And, secondly, as the alimentary particles can no 
longer be introduced through any point of the surface, a 
definite orifice is left in the membranous envelope, into 
which the nutrient materials are driven by the peculiar dis- 
position of the cilia; and, in many cases, a definite anal 
orifice is also provided, through which indigestible matters 
may be ejected. 
Thus, among the Protozoa, as among the Protophyta, whilst 
we trace a gradual advance in the differentiation of the homo- 
geneous particle of sarcode into the true cell, we find vast 
