90 BRITISH FRESHWATER RHIZOPODA. 
Body when at rest roundish or ovoid; at other times 
expanded, and during progression exceedingly mobile; 
the endoplasm a deep chlorophyllous green, with a 
pale marginal band, varying in width, of more or less 
clear granular ectoplasm; the pseudopodal filaments 
slender, branching and anastomosing, ultimately form- 
ing a widely-spreading network, colourless. Nucleus 
inconspicuous ; contractile vesicles (one or more) small, 
usually occurring in the semi-transparent ectoplasm. 
The bright green colour of the endoplasm, and its 
peculiar structure, distinguish Penardia from other 
Gymnomyxa with which it might be confounded. The 
predatory habits of the animal are also characteristic. 
This genus has been named in honour of Dr. Eugéne 
Penard, of Geneva, whose works on the Rhizopoda are 
so well known, and whose exploration of the Swiss 
lakes has brought to light many previously unknown 
species. 
1. Penardia mutabilis Cash. 
(Plate IX.) 
Penardia mutabilis Casa in Journ. Linn. Soc., Zool. XXIX 
(1904), p. 223, t. xxvi, ff. 1, 2 
Body when at rest roughly ovoid, with almost inert 
branching and anastomosing pseudopodia projecting 
from the surface at various points; the central mass 
opaque (semi-opaque near the periphery), without 
definite structure; at other times compressed and 
exceedingly mobile, the entire body expanding, elon- 
gating and contracting incessantly, and throwing out 
from different parts of the surface a widely-extending 
network of fine anastomosing pseudopodia which are 
used for the capture of prey. In this mobile condition 
the body becomes nearly transparent, and the endo- 
plasim is seen to contain a mass, with a well-defined 
general outline, of bright or yellowish-green corpuscles, 
oval in shape and closely compacted, but without 
apparent nucleus. Vacuoles appear in the ectoplasm, 
generally near the base of the branching pseudopodia. 
