362 CO. H. MARTIN. 
around. Cases in which either the stalk or the theca itself 
is bent are much more uncommon. 
‘px?-FIGURE 1.—Section showing relation of theca and stalk in 
Acineta papillifera. 
Cytoplasm.—The body of Acineta papillifera is pro- 
longed anteriorly and laterally into two lobes from which the 
two bundles of tentacles arise. In the individuals from 
Hickling broad there were almost always two vacuoles lying 
side by side. Of these, one appeared to be a true contractile 
vacuole with a period of about one minute, whereas the 
other appeared to act as a reservoir, maintaining a constant 
size about a quarter of that of the full contractile vacuole. 
In more or less starved forms the cytoplasm is quite 
hyaline, but in better fed forms the protoplasm may become 
very opaque owing to the presence of certain bodies with an 
affinity for nuclear stains. These bodies are apparently an- 
alogous with the ‘l'inctin-kérper of Plate VIII, the origin 
of which I have already dealt with in the case of Toko- 
phrya elongata. 
The macronucleus is generally an oval structure lying 
more or less centrally in the cytoplasm. Generally in whole 
stained preparations numerous spherical dark areas are to be 
seen resembling the so-called ‘ Binnen-kérper” of the 
Infusoria. In section these structures, as in the case of 
