Some Problems of Reproduction: a Comparative Study of ...

SOME PROBLEMS OF BE PRODUCTION. 43
nuclei of the conjugating cells. In this case the rejectionnuclei
would be of different generations, like the first and
second polar bodies.
In MONOCYSTIS Wolters has shown 1 that the nucleus of
either conjugating individual divides into two, a rejectionnucleus
which passes out like a polar body, and a gametonucleus
which fuses with that of the other individual.
4. Radiolaria.
In COLLOZOUM and SPHJEROZOTJM anisozoospores (of two
sizes) are formed, but are not known to conjugate. The size
of the anisozoospores is inversely proportioned to the number
of the brood. Both are formed by preliminary divisions of
the nucleus, and the resolution of the contents of the central
capsule into uninucleate swarmers.
5. Ciliata.
a. Free Ciliata and Suctoria.
The conjugation in this group differs from that in any other,
for in either gamete two pronuclei are formed, one of which is
exchanged for a pronucleus derived from the other gamete;
in each gamete the original and derived pronuclei fuse to form
a new nucleus; and the two separate without cytoplasmic
fusion, and after a time resume their normal life and fissiparous
powers. To understand fully this process we must premise
that the nuclear apparatus of the Ciliata is double, consisting
of a larger and smaller element, now termed meganucleus
and micr onucleus respectively. The meganucleus divides by
mere constriction, the micronucleus by a true mitosis, in fission;
and there is reason to believe that the meganucleus is the seat
of what we may term the physiological properties, the micronucleus
of the morphological or atavistic properties of the
single nucleus of other organisms. A fact that supports this
1 In 'Arch. f. mikr. Anat.,' vol. xxxvii, 1891, p. 91.