102 ZYGOPHYCER. 
simply by the growing together of the two conjugating cells, without 
contraction, and which do not rest, and (2) hypnospores (resting spores), 
which are formed by the partition of the zygospores, and which rest (as 
the name indicates) for atime before germinating. The Zygnemee and 
Desmidiew have, on the contrary, according to De Bary, spores of only 
one kind, namely, typical zygospores, in the formation of which a fusion 
and contraction of the whole protoplasmic contents of the conjugated 
cells takes place, and which become hypnospores without a preceding 
partition.” 
Wittrock adds:—‘ To me it seems perfectly clear that De Bary is 
quite right in saying that the hypnospores of the Mesocarpee are not 
analogous to the zygospores of the Zygnemew, or in other words, that 
they are not zygospores at all. The hypnospores of the Mesocarpee are 
formed by partition, and not by an immediate fusion of the protoplasm 
of conjugating cells, as the case ought to be with zygospores.” 
He then proceeds to refer to Pringsheim’s observations on this subject 
with commendation (‘“Jahrbucher” xi. 1877). “The act of conjuga- 
tion may be divided into two different stages. The first, being properly 
speaking only introductory, consists in the two cells which participate in 
the conjugation growing together by conjugation outgrowths, and the 
septum between the cells thus growing together being resorbed. This 
part of the act of conjugation is what Pringsheim calls copulation. The 
second stage consists in an intimate fusion taking place of the proto- 
plasmatic contents of the conjugating cells. This fusion is effected here 
in the Mesocarpee principally through the moving of the chlorophyll 
coloured parts of the protoplasm (the chlorophyllaceous bodies) into and 
to the neighbourhood of the somewhat widened conjugation canal. This 
second and more important stage of the fecundation Pringsheim calls 
connubium. The conjugation having taken place in this manner, its 
effect appears by the tripartition or quinquepartition of the cruciated or 
H-shaped cell formed by the copulation. Of the cells formed by this 
partition, the central one is fertile, the two or four lateral ones sterile. 
The result of the conjugation is consequently not one cell, but several 
cells, and not cells of one kind, but of two, namely, one propagative cell 
(a spore), and around it two or four cells not capable of germination. It 
would be difficult to find a reasonable interpretation of such a result, save 
the one suggested by Pringsheim, of its being a sporocarpium, and to me 
this interpretation seems not only reasonable, but perfectly natural, for 
although the sporocarpium does here remain ona very low, not to say 
the very lowest, stage of development, it does, however, already possess 
the constituent parts of a typical sporocarpium. It has a nucleus and 
@ pericarpium, or at least an equivalent to one. The nucleus is the 
single central spore-cell, and the ,pericarpium is represented by the two 
or four lateral sterile cells.” 
“Tf the explanation given above is accepted, the essential difference 
betreen these Alga and their nearest relations, Zygnemew and Desmi- 
die, might be expressed in the following manner:—The result of the 
connubium in the former is a sporocarpium (and their spore is conse- 
quently a carpospore), but the result in the latter is a zygospore.” 
Wittrock then proceeds to show that in one species the formation of 
the spores can take place equally in the manner of Mfesocarpus, Plagio- 
spermum, and Staurospermum, equally by tripartition, quadripartition, 
and quinquepartition, and hence he concludes that those genera are not 
sound, and that all three should be included under sub-sections of the 
same genus. We have not followed this suggestion, but have retained 
Mesocarpus and Staurospermum as distinct, relying upon the difference 
of form in the central cell. 
For further details we refer the student to the Memoir from whence 
the foregoing observations are abstracted. 
