202 
NOTES AND MEMORANDA. 
tuting for the brass plate a Barker’s revolving selenite stage, by 
means of which the disk-holder can be readily rotated.* 
Terricolous Bhizopoda. — M. A. Schneider has presented through 
M. de Lacaze-Duthiers to the Academy of Sciences the following 
note : — 
It is known that some rhizopods are able to live on land. De 
Greeff has described six or seven species — Amoeba terricola and Arcella 
arenaria amongst others. We have found these latter forms and ten 
others incontestably new, and all belonging to the group of Amoebaa 
furnished with a test. The test has more or less the form of an 
ovoid, sometimes drawn into a neck at one of its extremities, and 
nearly always compressed so as to present two distinct faces. It appears 
to be chitinous, sometimes thin and transparent, and figured with 
hexagons, areoles, circles, &c., sometimes thicker and coloured brown, 
and in a very common Arcella formed as if by an agglomeration of 
small grit. It has only one orifice smooth or indented, terminal or 
situated on one of the faces bevelled out to receive it. 
The sarcode body of the interior, observed in a state of repose, is 
clear and homogeneous without granules in its lower third part, which 
encloses only the nucleus and two or three contractile vacuoles. At 
the limit of this lower third and the two upper thirds is seen a layer 
of fine yellowish granules spread out in a transversal plane. The two 
upper thirds are formed of a protoplasm more or less irregularly 
granulous, with or without foreign bodies in process of digestion. 
The nucleus, always spherical, encloses one or many nucleoles. 
When the animal is active this distribution of its constituent 
elements is disturbed, and it is seen to emit by the orifice of its shell 
pseudopodia which resemble in their general features those of the 
amoeba, and whose length may reach to double that of the shell. To 
emit these pseudopodia the animal detaches itself more or less from 
the internal walls of its habitation, to which it only adheres at various 
points by protoplasmic filaments. 
If the exterior conditions become unfavourable the rhizopods 
retract and encyst themselves. In the interior of the shell is then 
seen a regular sphere, in which all the elements of the structure of 
the animal are recognized, enclosed with foreign bodies. 
A certain number of these expelled before the encystment may 
form a protecting barrier at the orifice of the shell. On adding a 
little water they are seen to break the frail envelope of their cyst and 
to resume possession of their quarters. 
We have seen conjugation in the case of four of the species, and 
there is reason to believe that it occurs in all. 
To this conjugation succeed cysts whose contents represent some- 
times those of the two contractants ; sometimes those of one only; 
each one then encysting for itself after an ephemeral union with the 
other. 
These cysts of reproduction give spherules or spores, the evolution 
of which we have not yet followed, but which we hope to be able to 
* ‘ English Mechanic,’ vol. xxvii. p. 370. 
