6 BRITISH FRESHWATER RHIZOPODA. 
Tests with lobed apertures, such as those of Difflugia , 
corona, D. oviformis, and D. lobostoma, show a con- 
siderable variation in the shape or number of the lobes, 
but are nearly always symmetrical. 
Considering the manner in which Rhizopoda con- 
struct their tests, the bi-lateral symmetry they nearly 
always possess is very remarkable. Attention however 
may be directed to one departure from this in the case 
of curved tests, belonging to species which usually 
possess them straight, found occasionally in very 
restricted habitats; one such, Difflugia acuminata 
var. curvata Cash, is described in Volume I, and the 
writer found in a pond in Long Jsland, U.S.A.,* two 
species of Nebela and a Quadrulella thus modified, 
and in Georgia, U.S.A., a curved species of Arcella 
occurs. 
Reproduction in the Rhizopoda usually entails and 
at certain stages may entirely consist of either multiple 
or simple binary division. In the latter case the test, 
if it is membranous or chitinous, may also divide, a 
process which nearly always takes place in a longi- 
tudinal direction; the more substantial tests, such as 
those of the Difflugi# and Nebelx, do not divide. In 
Volume III, Plate LIII, fig. 4, is an illustration of the 
division of a test of Diaphoropodon mobile, and Plate 
LVII, fig. 4, depicts what appears to be the commence- 
ment of division in a transverse direction of a test of 
Amphitrema flavum. 
In some genera or species the tests are protected by 
a more or less thick covering of very fine hair-like cils 
which appear to be secreted from the interior through 
fine pores, as for instance Diaphoropodon mobile, Nebela 
Larbata, and species of Cochliopodium ; and from Sierra 
Leone a species of Difilngia has been recorded bearing 
fine spines; even one or two amceboid species are 
thickly covered with very fine cils which disappear 
and re-appear as the plasma flows, and must therefore 
be protrusions of the plasma itself, e.g. Amabu pilosa. 
* », * Journ. Linn, Soe., Zool.’ vol. xxxii, pp. 136, 142. 
