Anatomy of Nyctotherus ovalis. By W. C. Bosanquet. 405 
seemed in all cases to have shrunk away from the wall of the vesicle 
in the process of hardening. This body occupied always the same 
position just above the nucleus of the animal, and could be seen in 
specimens mounted whole, though it was not very apparent until 
closely looked for. It was found in all the well-preserved specimens 
of the smaller-sized Nyctotherus; in the large specimen (plate IX. 
fig. 5) a slightly different appearance was seen, a body being found in 
the same position, hut resembling the rest of the nucleus in structure. 
This is probably the micronucleus of Nyctotherus ovalis, a body which, 
according to Btitschli (2) is probably present in all Ciliata, with the 
exception of the Opalininae and multinuclear forms. He states that 
“ it is generally single, and situated close to the surface of the macro- 
nucleus; in shape it is spherical or ellipsoid, and in size it varies 
from 1 to 10 /-t in its longest diameter. Structurally it consists of 
a delicate membrane, often brought out very distinctly by reagents 
which coagulate the contents. These sometimes appear attached to 
one pole of the membrane, at other times lie free in the centre, and 
are either homogeneous or form a finely granular reticulum. In 
the elliptical micronuclei there seems to be a differentiation of the 
contents into staining and non-staining substances (chromatin and 
achromatin).” 
Kent (4) states that in Nyctotherus ovalis there is no distinct 
endoplastule, and Stein (1 ) says that a nucleolus is not to be found 
in this animal ; nor can I find any allusion made to a micronucleus 
in this Protozoon, except by Maupas ( 8) who notes that “ it is de- 
prived of affinity for colouring matter.'’ In Nyctotherus cordiformis 
Stein and Schneider (5) describe a nucleolus separated from the 
nucleus by a considerable interval, situated, according to the illustra- 
tions, between the nucleus and the pharynx. The latter observer 
notes that it is one of the smallest micronuclei in existence, and lays 
special stress on its separation from the macronucleus. 
Macronucleus . — The different appearance presented by the macro- 
nucleus in different specimens is shown in figs. 3, 4, 5 and 6. In 
some cases, as in fig. 4, it is small, more or less spindle-shaped in 
section, and filled with small round bodies which stain deeply with 
haematoxylin, their size and number varying in different specimens. 
These are named by Schneider (5) “ chromatosplierites,” and were 
described by him as being isolated bodies, not the optical effect of the 
nodes of a filament or network, as Biitschli seems to regard them ; 
that the former is the case seems proved by the specimen shown in 
fig. 4, in which one of these bodies has fallen out of the nucleus into 
the surrounding protoplasm. They are regarded by Khumbler (6) 
not as organised structures, but as masses of storage material formed 
by the coagulation of a substance which is at first fluid, then becomes 
viscid, and finally solid. In other specimens, as in fig. 6, the nucleus 
is much larger, unstained by haematoxylin, and presents a granular 
appearance. 
