89 MaynArD M. METCATF, 
mass of small eoceus-like granules entangled in the posterior cilia 
or dragging in an irregular strand behind the animals as they swim. 
The well developed excretory vacuole of O. intestinalis, O. caudata, 
or of an undescribed species I am now studying, occasionally contracts, 
extruding granules from the excretory pore at the posterior end 
of the body. Probably all eylindrical species of Opalina have well 
developed vacuoles. In the flattened species the vacuoles are reduced 
or absent. None of the specimens I have show any special mass 
of granules among the cilia at the posterior end of the body, but 
preserved specimens of 0. intestinalis or 0. caudata almost never 
show the extruded granules. 
The cilia show no unusual features. 
It is in the nuclei of this Opalina that the phenomena of chief 
interest are seen. Opalina mitotica is a binucleated form, but each 
of its nuclei, under ordinary conditions, is dumbbell-shaped and is 
seen to be resting in a late anaphase of mitosis (Figs. 1—5 and 14). 
None of my specimens show the mitotice phenomena as clearly as 
could be desired. The nuclei stained with carmine are not at all clear 
even when examined by green licht, and those stained in CoNKLIN’S 
picro-haematoxylin do not give nearly as good results as are obtained 
in Opalina intestinalis and O. caudata by heavily overstaining with 
DerArıEenv’s haematoxylin and decolorizing rather rapidly under the 
microscope. Counts of the chromatin masses (chromosomes) have 
been made for one or both nuclei in about twenty-five of the more 
favorable individuals. The number seems to be ten, though none 
of the nuclei show their structure with the absolute clearness 
desirable for counting such irregularly shaped chromosomes (Figs. 7, 
9 and 14). I have however no doubt of the correctness of the counts. 
The irregular form of the chromosomes reminds one of conditions 
in O. intestinalis and O. caudata, as does also the character of the 
fibres of the mitotie spindle and the appearance of the whole mitosis 
(Fig. 9). In one nucleus there was found a fusion of the chromosomes 
into a ring (Fig. 13), as is so characteristic of the late anaphase 
stage of mitosis in O. intestinalis and O. caudata, especially if these 
animals have been kept for a few days outside the host in normal 
salt solution. The same phenomena of fusion of the chromosomes 
is often seen in nuclei of freshly taken Opalinas of the two species 
mentioned. It seems to be a normal phenomenon which is emphasized 
under abnormal conditions. In O. saturnalis, as described by LEGER 
and Dusosc, the chromosomes at one stage form a ring around the 
