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

SOME PROBLEMS OP REPRODUCTION. 7
isogamy. By endogamy I imply the union of gametes from a
single gametogonium, by exogamy their union with those
from other oogonia exclusively. Portions of the nucleated
or non-nucleated protoplasm, left out in schemes of gametal
formation, are termed epiplasm. I have found it useful to
introduce the following notation to denote relationship among
nuclei, viz. to use a given letter for the parent nucleus, and the
same letter with that figure as an index which denotes the
number of bipartitious that have taken place, to denote a
brood-cell issuing from those bipartitions; thus if N be a
nucleus, N 5 will denote a brood nucleus of the 5th bipartition
of N; the notation is abbreviated, N" denoting N-r-2 a .
II. TYPICALLY AGAMIC REPRODUCTION.
Before examining into gametogeny we must note the-existence
of a group of organisms which appear to be essentially
agamous. I refer to that of MYCETOZOA, including the
Monadineae of Cienkowsky, the Acrasiese, and the Myxomycetes
proper.
In the MONADINEJE, a group relegated with exceptional
liberality by the zoologists to the botanical " sphere of influence,"
we have a very primitive group, most species having
the three forms of Mastigopod, Myxopod, and Cyst, beside a
Resting Stage, which is never preceded by karyogamy. The
adult forms may become plurinuclear or fuse into plasmodia
like the Myxomycetes, but no nuclear union takes place;
nay, even in the plasmodia further nuclear divisions may
occur.
In the true MYXOMYCETES, plasmodial fusion always precedes
spore formation. Possibly, as has often been suggested, plasmodial
formation has led to the various modes of karyogamy.
The nuclei pass freely from place to place in the plasmodium,
and may eventually be far removed from what was their original
cytoplast; and the cytoplastic elements again undergo a
reorganisation by their fusion, which we may term plastogamy.
In this way is fulfilled what I regard as the object