Opalina. 291 
eight chromatin masses which were donbtless eight chromosomes 
(Figs. 201—203, Pl. XXIV), showing that the nuclei were syncaria 
resulting from copulation. 
Copulation may occur while the single nucleus of the macro- 
gamete is in division. In this case the male nucleus waits until 
the division is complete and then fuses with one of them, the 
anterior one in the best case I have observed (Fig. 200, PI. XXIV). 
Both nuclei of the macrogamete may be in division when cop- 
ulation takes place. One preparation showing this condition was 
very clear (Fig. 204, Pl. XXIV). The male nucleus, by its longitudinal 
striation and the position of its chromosomes in two polar groups, 
showed that it also was dividing. A second preparation shows a 
zygote in division with each of the femali nuclei already divided, 
giving four daugther nuclei and the male nucleus, in an early stage 
of mitosis, lying beside them (Fig. 208, Pl. XXIV). Under perfectly 
normal conditions division of the cell-body of this animal should 
have occurred before the complete division of the nuclei. Another 
preparation of a daugther cell’) just from division and whose nucleus 
was in a little later telophase than the female nuclei in the next 
to the last case, showed a male nucleus lying against the constricted 
portion of the dumbbell-shaped female nucleus (Fig. 206, Pl. XXIV). 
This male nucleus was in a very early anaphase stage of division. 
It must have entered before the division of the macrogamete and 
have passed to one of the daughter cells (cf. Fig. 204, Pl. XXIV). 
I have seen two instances of another condition which may pos- 
sibly stand as the next term in this series of copulation conditions. 
These individuals seemed each to show four nuclei. In one instance 
the four nuclei were in an oblique row (Fig. 207, Pl. XXIV). As 
the posterior end of the body showed a slight division-furrow, it 
is somewhat doubtful if this was a zygote. It may possibly have 
been a dividing binuclear macrogamete in which the dumbbell- 
shaped nuclei overlapped, somewhat more than in Fig. 204, Pl. XXIV, 
producing in edge view the appearance of four nuclei. The pre- 
paration, stained with acetic-carmine was not entirely clear. The 
other instance was of a living animal, a dividing macrogamete, 
with a considerable division furrow at its posterior end (Fig. 209, 
Pl. XXIV). It seemed to show four unusually small nuclei side by 
side in pairs, but the picture was not very clear. Both of these 
*) That it was a daughter cell fresh from division was indicated by the 
irregular contour of one side, the side by which it had been attached to its 
sister cell, 
