192 ARCHER, ON SPIROTANIA,; 
were there as before, which, combined with the solitary band 
of endochrome and the cylindrical figure, tapering towards 
the ends, rendered it without doubt that it was one and the 
same plant. I was much pleased, therefore, to find this very 
distinct species a second time after so long an interval, 
especially in the conjugated state, forming, indeed, the second 
known instance of conjugation in the genus. 
I have alluded to the recent work of Reinsch, in which he 
denies to “‘ Palmoglea macrococca”’ (Kitz. )—more properly, 
surely, regarded as a species of Mesotenium—a place amongst 
Desmidiacee, and this because he believes the plan of conju- 
gation in that plant to hold a middle place between that of a 
typical Desmidian and the Zygnemacee. He holds that each 
parent-membrane of the conjugating cells of Mesotenium 
(which, notwithstanding the heterogeneous and incongruous 
character of Kiitzing’s genus Palmogleea, he stills calls by 
the latter name) actually takes a share in the formation of 
the zygospore itself, nay, even that the two coalesce so as to 
form its special membrane, and that hence it cannot be placed 
with Desmidiacee on the one hand nor with Zygnemacez on 
the other. At least, then, a place in the Desmidiacee could 
not be refused to Spirotenia condensata nor to S. truncata on 
the same grounds. Here, manifestly, the parent-membranes 
take no share in the formation of the zygospore, not even so 
much as to form a connecting canal, as in Spirogyra or 
Zygnemacee generally. But, though it may be in a measure 
apart from the subject proper of this communication, I can- 
not refrain from expressing my conviction that Reinsch is in 
error in the view he expresses as regards the process of con- 
jugation in Mesotenium (Palmoglea macrococca, Kiitz.). I 
venture to say that here the membranes of the parent-cells do 
not take a part in the formation of the zygospore, but that 
during the conjugation they are gradually thrown off, and 
probably become dissolved and help to increase the surround- 
ing gelatinous matter. They, in fact, come away, leaving the 
contents to become mutually fused, quite as they do in Penium 
or in Cylindrocystis, only they are more fugitive. See on 
this point De Bary’s figures* in Mesoteenium as well as — 
Cylindrocystis, which genera, along with some others, as 
well as some as yet uncertain forms, make up the old incon- 
gruous genus Palmogloea (Kiitz.). I venture to think that 
Reinsch, the next time he examines. some of these plants 
* © Untersuchungen, &c.,” t. vii; also my own communication, ‘ Proceed- 
ings of the Natural History Society of Dublin,’ vol. iv, p. 12, pl. i, figs. 8— 
14, Mesotenium, and 35—44, Penium ; also ‘ Quarterly Journal of Micro- 
scopical Science,” Vol. IV, N. 8., p. 109, Pl.. VI. 
