ARCHERINA BOLTONI. 115 
plasmodium, that is to say, is not formed by fusion of 
independent amoeba forms, but is due to continuous 
erowth. When nutrition fails, the individual chloro- 
phyl corpuscles separate, each carrying with it an 
investment of protoplasm, and then each such amceba 
form forms a cyst around itself, which is covered with 
short spines. The cysts are not known to give rise to 
spines, but appear to be merely hypnocysts. The 
domination of the protoplasm by the chlorophyl cor- 
puscles is very remarkable and unlike anything known 
in any other organism. Possibly the chlorophyl cor- 
puscles are to be regarded as nuclei, since it is known 
that there are distinct points of affinity between the 
dense protoplasm of ordinary nuclei and the similarly 
dense protoplasm of normal chlorophyl corpuscles.” 
Order II. CONCHULINA. 
Family 1. ARceLuipa. 
Test simple, transparent, homogeneous, or composed 
of numerous and variously-formed chitinoid plates, or 
opaque from encrustation with sand-grains or other 
extraneous material; monothalmous; pseudopodia 
mostly digitate, rarely lobular; nucleus single or mul- 
tiple; contractile vesicles one or several. 
SYNOPSIS OF THE GENERA. 
Test discoid, membranous; in dorsal view circular, 
laterally hemispherical or depressed ; mouth central. 
15. Arcella. 
Test discoid, circular, flexible in the young state, the 
outer lamina extremely thin; oral aperture irregular 
and rarely distinguishable. 16. Pseudochlamys. 
Test discoid, with a circular or broadly oval, some- 
times irregular outline, obtusely rounded and thickened 
posteriorly ; the oral aperture excentric, round, oval, 
or lobate. 17. Centropyzis. 
