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

SOME PROBLUMS OF REPRODUCTION. 19
but the zoospores, formed by the resolution of the protoplasm
into uninucleated cells, have nuclei constituted by the fusion
of several vegetative nuclei. We may, however, regard this
multiple fusion of nuclei as a karyogamic process, and the
zoospores as zygotes issuing from multiple endogamy. This
process is a further development of the gametogeny of Dasycladus;
and we shall find that the Saprolegniese and Peronosporese
have similar relations with one another.
SPHJE&OPLEA, 1 like Cladophora, has chambered filaments, and
each chamber is subdivided by protoplasmic septa, in which
alone the nuclei lie, from one to four in each. The plant is
oogamous. The spermatozoa are formed in distinct chambers
to the oospheres; to form the former rapid nuclear fission takes
place in each protoplasmic septum, which is finally resolved
into the numerous uninucleate spermatozoa, the parietal
protoplasm being also used up in the process.
The oospheres are also formed by the rounding off of the
protoplasm into numerous uninucleated spheres without epiplasm;
perforations are formed in the wall of the tube to admit
the spermatozoa, but how or at what stage is not stated. The
oosphere-nucleus is formed by the fusion of several nuclei.
Rauwenhoff writes, 3 " The number of nuclei seems to diminish;
each aggregation of protoplasm possessing three or four
chromatophores, .... while I only found one or two nuclei.
When there were two, they were closely appressed; when a
single one, it was large and elongated. In either case the
nucleoli had disappeared; the chromatic elements were visible
as dots or rods, aggregated in an irregular figure. To all
appearances, then, several nuclei fuse into one." This account
might almost fit word for word the phenomena seen in the
formation of the oospheres of Saprolegnia.
1
"Zur Kenntniss der Algengattung Sphseroplea," in ' Berichte d. Deutsch.
Bot. Gesellsch./ vol. i.
2
"Recli. sur le Sphseroplea annulina," in 'Arch. Norland.,' vol. xxii,
1888. This later paper I only saw during the correction of the proofs. I
had, in the MSS., anticipated the probability of nuclear fusion in the
oospheres, despite Heinricher's statement to the contrary.