INFUSORIA PARASITIC IN CEPHALOPODA. 189 
posed of the epithelial cells of the kidneys of the host. We 
do, indeed, see remains of cells in all stages of digestion 
(cf. fig. 8), and a careful examination of many different 
individuals has brought me to the conclusion that the majority 
of the chromatin particles in Chromidina are the remains 
of the nuclei of renal cells. 
These ingested particles may be very strikingly demon- 
strated by staining the animal with neutral red intravitam 
(fig. 5). The nuclear net remains unstained. 
It is possible that the chromatin particles also constitute, 
in part, the micronucleus of the infusorian—the network 
representing the meganucleus. Multiple micronuclei are 
known in other Infusoria—e.g.in Loxodes, (cf. Joseph, 11). 
Regarding the second question, I think there can be but 
little doubt that all the animals which show irregular lumps 
or granules of chromatin, in place of the delicate nuclear net- 
work, are abnormal. The appearances are caused by imper- 
fect fixation. Almost immediately the animal dies, or is 
allowed to dry ever so little, the network breaks up, and its 
parts run together to form irregular chromatin masses. This 
can be easily proved by merely letting a smear preparation 
dry slightly in the air before fixation. The granular masses 
of chromatin then appear in nearly every individual in the 
preparation, after fixing and staining (cf. fig. 7). 
Even in a well-preserved specimen it is often impossible to 
find the chromatin of the nuclear net continuous—because 
the distribution of the chromatin in the plastin network, which 
forms the basis of the nuclear apparatus, is not uniform. This 
is especially obvious in specimens which have been treated by 
a method involving differentiation after staining—e. g. iron- 
hematoxylin or borax carmine. ‘The smaller masses of 
chromatin become decolorised before the larger—which 
apparently lie freely in the cytoplasm, though really imbedded 
in the plastin network (see fig. 1). 
It is surprising that the nuclear apparatus in the head of 
the organism—when of large size—should have passed 
unnoticed. It is a most striking structure in the form of a 
