SOME OBSERVATIONS ON ACINETARIA. 371 
in fig. 5 the remains of three degenerating micronuclei are 
to be seen. 
In Pl. VII, fig. 6, the conjugating processes of the same 
pair are seen under a higher magnification. In the right-hand 
form the spindle of the fused male and female pronuclei is 
already formed. In the left-hand form the female pronucleus 
is lying close to the partition separating the two conjugants, 
whilst the male micronucleus is in a depression between the 
two conjugating forms. 
This stage seems to be comparable with that figured by 
Hickson for Dendrocometes, Pl. 17, fig. 10, and shows 
that here, as in Dendrocometes, in contradistinction to the 
state of affairs found in Paramecia, the male and female 
pronuclei fuse not in the spindle, but in the resting stage. 
It is also interesting to find that here, as in the case of 
conjugation in Didinium nasutum described by Prandtl, 
the male pronucleus seems to be considerably smaller than 
the female pronucleus. 
The later stages in conjugation become exceedingly diffi- 
cult to follow, as the chromatin of the macronucleus seems to 
be dissolved out of the achromatic network, and to be scat- 
tered through the cytoplasm in the form of darkly-staining, 
irregularly spherical blocks. 
Normally, the zygote nucleus formed by the fusion of the 
male and female pronucleus appears to divide twice in suc- 
cession, and of the products of this division two degenerate 
—one becoming the new micronucleus, and one the new 
macronucleus. 
In Pl. VII, fig. 7, the achromatic network of the old 
macronucleus (Ma.f.) is still to be seen, though nearly all the 
chromatin appears to have been dissolved out, and to he in 
irregular blocks (Chr.) in the cytoplasm. 
Two of the division products of the zygote nucleus are to 
be seen as faintly stainimg vacuolar bodies, both closely 
applied to a mass of chromatin (Mz.). This relation suggests 
the absorption of the dissolved chromatin by the growing 
nucleus, a process to which Hamburger has drawn attention 
