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

SOME PROBLEMS OF REPRODUCTION. 15
cerned in this process degenerates into mucus, while the rest
rounds off, awaiting fertilisation. This process is obviously a
purely adaptive one, destined merely to favour the approach
and entrance of the spermatozoon.
Similar " excretions " occur elsewhere for similar purposes;
thus in Peronosporese, Saprolegniese, and Chytridiese
the asexual zoosporange forms a beak for the discharge of the
zoospore; in Chytridiese the protoplasm which fills this beak
undergoes degeneration; while in. Saprolegniese it is retracted
and absorbed into the body of protoplasm not yet fully
differentiated into zoospores. In the Chytridian Woronina
polycystis, which I have studied myself, the formative protoplasm
of the beak contains a nucleus, and appears to be a
zoospore degraded for the purpose of opening a gate to its
sisters. 1 Hence neither physiologically nor morphologically
can excessive stress be laid on such a degradation, whether of
cytoplasm or nucleated protoplasm.
The spermatogonia of Oedogonieae are formed by repeated
bipartitions of the vegetative cells, and are short and
discoid. In each spermatogonium the protoplasm rounds off
and divides to form two naked spermatozoa; or this division
is suppressed, and the protoplasmic body of the spermatogonium
escapes as a single spermatozoon. The spermatozoa
have, like the asexual zoospores, a subapical ring of cilia, but
are smaller. In certain species the discoid cells produce not
spermatozoa, but so-called " androspores," of similar character
but of different fate. For the androspores settle on the base
of the oogonial cell-wall and develop into " dwarf male"
plants; all the cells of these (save sometimes a sterile basal
cell) are spermatogonia, and behave like the same organs in
the other species. This is the first case in which we find sex
anticipated by or reflected back upon individuals or
organs antecedent to the gametogonia. 2
1
As stated by me in a communication to Section D of the British Association
at Leeds, 1890, Report, p. 872.
2
The colonies of Eudorina and some forms of Volvox only produce
gametes of one sex, but have no other peculiarity to distinguish them.