214 ARCHER, ON CYLINDROCYSTIS, 
primary cells of the following generation, however, in each 
differ in what I should but regard as a secondary and un- 
essential circumstance, in that in Gidogonium and Bulbo- 
chete they are for a time motile, whilst in the parallel 
degree of development of the spore of Cylindrocystis and 
Mesotzenium they are, as always, still. 
Examples of conditions nearly as simple are presented by 
many Desmidiacee, but also conditions more complex are 
met with in various species, to enter into detail here as to 
which would, however, be superfluous. Many of the zygo- 
spores become, as is well known, furnished with variously 
fashioned spine and processes, which circumstance seems to 
me probably to find a parallel in the less developed ones of 
(Edogonium echinospermum. As is well known, very varied 
conditions are to be met with appertaining to, and charac- 
teristic of, various species. Thus, the spinous or non-spinous 
zygospores—the simple or variously branched spimes—the 
orbicular, or quadrate, or characteristically lobed figure of 
the zygospore—the relative positions of the conjugating pairs 
of individuals—the, so to say, double spore of -Closterium 
lineatum—the conjugation following immediately on self- 
division in Closterium Ehrenbergiu, C. Pritchardianum—the 
complete and persistent fusion of the parent-membrane in 
Hyalotheca dissilens, Closterium parvulum—the remote outer 
coat of the spore of Tetmemorus levis, &c., besides minor 
specialities of detail proper to the various forms—all these. 
can hardly be considered as the accompaniments of an acci- 
dental phenomenon, in itself meaning nothing, and destitute 
of significancy. 
But, in pursuing onward our examination of the conjuga- 
tive process and its results, the behaviour in Didymoprium 
Grevillii, in which species, of two conjugating filaments, the 
cells of one are always the receiving, those of the other the 
giving, cells in the conjugative act, leads us to Spirogyra, in 
which these conditions are constant. In this latter genus the 
receiving cell frequently assumes an enlarged and different 
figure, often preparatory to, and in anticipation of, the acces- 
sion of the contents of the giving cell, thus, I think, exhibit- 
ing a certain significant amount of differentiation. 
In Spirogyra and Zygnema, as is well known, the act of 
germination consists in the inner coat of the zygospore ex- 
panding and bursting off the outer, and, while extending in 
length, becoming transversely divided by a septum, the lower 
cell remaining always undivided as a “ root-cell,” the upper 
becoming the first ordinary joint of the new plant, thus dif- 
fering from Cylindrocystis and Mesotenium. But in this 
