82 BRITISH FRESHWATER RHIZOPODA. 
Body discoid, distinguished by the vacuolation of its 
protoplasm, and the presence, within it, of reniform 
concretions; also by its large, block-like, tesselated 
nucleus, and the peculiar hernia-like pseudopodia, 
which appear to burst with a sudden action through 
a toughish cortical layer. Contractile vesicle central. 
Dimensions; About 125 » in diameter (Ray Lan- 
hester), 
In ponds near Birmingham, discovered by Mr. 
Thomas Bolton. 
In his description of Lithameba (loc. cit., 1879), 
Professor Lankester says that the pseudopodia differ 
from those of Amewba, being rounded and lobular, 
never digitate, resembling rather “the hernia- like 
extensions of the protoplasm exhibited in Pelomya.” 
It is easy, he says, to recognize a distinct pellicle, or 
temporary cuticle, which is formed upon the surface 
of the protoplasm and bursts when a pseudopodium is 
formed. In fact it is the rupture of this pellicle which 
appears to be the approximate cause of the outflow of 
protoplasm as a pseudopodium. “ Probably a. still 
more delicate pellicle forms on the surface of the 
naked protoplasm, and, in the way just indicated, 
determines by its rupture the form and the direction 
of the ‘ flow’ of protoplasm which is described as the 
protrusion of a pseudopodium.” 
Prof. Lankester discovered an excessively fine reti- 
culate or vacuolar surface-structure. This differentia- 
tion of the protoplasm, he says, can be detected all 
round the margin of the disc-like body, in fact wher- 
ever the protoplasm is sufficiently free from concre- 
tions, or food-matter, to allow of proper illumination 
or inspection. The numerous concretions which may 
be seen imbedded in the endoplasm are minute, with 
a tendency towards a reniform outline. These bodies, 
he thinks, are only a larger form of the refringent 
granules which are present in great quantity in the 
protoplasm of the common large Anuwrda, 
