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

42 MAROUS M. HARTOG.
of further vital evolution. In Dallinger and Drysdale's group
the whole zygote is resolved into uninucleated spores; and
the process in Noctiluca is a mere modification of the
same process.
2. Rhizopoda and Heliozoa.
Conjugation is known to occur in some members of this
group; the gametes appear to be ordinary individuals; but we
have no full knowledge either of the antecedent or consequent
processes.
3. Gregarinida.
The details of conjugation in this group are not fully made
out, but that of OPHRYOCYSTIS is interesting. In this genus the
apocytial body is first resolved into uninucleate cells, which conjugate.
The two nuclei are stated not to fuse, but to give
rise to six, two of which unite to give rise to a zygote-nucleus,
around which the cytoplasm aggregates, while the other four
nuclei pass to the peripheral cytoplasm, which degenerates
with them. Obviously the conjugating cells are progametes,
which only develop gametonuclei afterwards; and of these
last, two only are functional : the peripheral cytoplasm
and the other four nuclei represent arrested gametes. It
would be interesting to know if the tripartite division of
the nucleus of each of the conjugating animals corresponds to
the schema annexed (Fig. 5), where N, M, represent the
M
N
i
3
_
M l
FIG. 5.—Tentative schema to explain the conjugation of Opbryocystis.
N, M, are the primitive nuclei of the conjugating pair ; successive stages
are separated by dotted lines, and the rejection-nuclei are surmounted by
dashes; the square encloses the zygote-nucleus Z, formed by the union
of N s , W.