20 
eule firm, membrane loosely investing the endosarc, and following its 
movements ; it is very extensile, so that it spreads over the pseudopodia as 
it spreads outwards, until quite thin and colourless, whereas it is ordinarily 
of a yellow tint. It has vacuoles, but no nucleus was observed. 
Another Rhizopod is mentioned by Greef, which, resembling in form and 
color the Arcella vulgaris, a water species, is named by him Arcella arenaria, 
It is found in sand under mosses, liverworts, &c. &c. It measures -~ 
inch in size; its surface is smooth, not marked as A.. vulgaris, by a network 
of regular lines ; its color is deep brown, inclining to yellow. It possesses 
numerous pseudopodia, projecting everywhere from its surface; these are 
lobed, or digitate with pointed extremities. The movement of the sarcode 
is very active. 
Much as I have shortened Dr. Greef's account of these new genera and 
species, I yet fear that I have exhausted the patience of my hearers. I 
reserve therefore for another occasion a notice of Cienkowski's observations 
on Monads. The only point to which I now, in conclusion, would direct 
your attention is this,— that the typical Amoeba, and also all Amoeboid 
forms of the Protozoa, stand at a considerably higher point in the scale 
than the class Monera of Haeckel. This accurate observer and lucid writer 
restricts his definition of Monera to creatures which consist solely of naked 
protoplasm, without vacuole or nucleus, and are entirely destitute of any 
organization whatever, no difference of internal and external molecular 
constitution being perceptible, whereas our land and water Amoebae have 
distinct generative organs, and their mode of reproduction closely approaches 
that of the Infusoria. In particular, the differentiation of the substance of 
the nucleus and development of L ova, possibly even of sperm, as well as 
germ elements, reminds us of Balbiani's account of the sexual organs of 
Infusoria. 
The morphological unit known as a cell, with or without membrane, can 
no longer be regarded as the primary or simplest form of living matter, and 
all unicellular organisms may be said to have already reached a definite 
standard of organization. Amoebae, Arcellae, &c. present a recognisable type, 
which apparently prevails throughout a large series of the lowest Protozoa, 
and from which, as a point of departure, we can trace progressive evolution. 
But in the group Monera we arrive at organic matter which may be either 
vegetable or animal, for no boundary line can be drawn where there fs 
nothing to mark the limit. A definition founded on usual criteria of struc- 
tural adaptation or characteristic function is no longer possible. Physio- 
logically, indeed, we may perhaps assign the ingestion of foreign bodies, and 
particularly the digestion of animal matter, as an indication of animal 
