ARCHER, ON SPIROTANIA. 19] 
arranged short, linear spines of that structure form to the eye 
a kind of border, which momentarily might be thought to re- 
semble the border produced by the honeycomb structure on 
the zygospores of Spirotenia condensata ; and the bodies them- 
selves are, moreover, much about the same size. The prevalent 
occurrence in pairs, too, of the former, after the original wall 
of the Penium has disappeared, might help to lend them a 
further resemblance. But I need hardly insist on their wide 
distinctions when carefully viewed, yet it is, perhaps, not 
quite out of place to draw attention to these very different 
structures simultaneously. 
As regards the second species of Spirotenia which it has 
been my good fortune to find conjugated, Spirotenia truncata 
(mihi),* 1 regret that I cannot give any account of the early 
stages of the process. I am only in a position to offer a 
figure of the fully formed zygospore. Here, as in by far the 
most of the Desmidiex, there is one spore only formed. It 
is, however, of a novel form, so much so as that I feel satis- 
fied it could not be mistaken for that of any other species 
whatever yet known, nor for any other described unicellular 
structure. The zygospore here is equally lobate, the lobes or 
projections being of a triangular or conical outline, the apices 
subacute; there are no spines; the tint of the cell-membrane 
appears to be of a kind of straw colour, and the contents 
seem to form a globose mass in the centre, leaving the 
angular lobes void. The four empty halves of the pair of 
parent-cells seem to remain loosely appended, each pair dia- 
metrically opposite tothe other, the zygospore between (fig. 12). 
As regards the plant itself in the unconjugated state, I 
might mention that the cells seemed to be somewhat more 
minute than when I saw it on the first occasion; also the 
spiral band was rather more narrow and definitely margined, 
and sometimes appeared to branch or subdivide, and the 
enveloping gelatinous envelope was less marked. ‘The 
latter circumstances might, perhaps, be accounted for, as in 
S. condensata, by the gathering in which they were detected 
being for some time in the house. But though the spiral 
band was more sharply defined, and any scattered granules 
likely to impede the view into the interior of the cavity of the 
cell were likewise fewer than when I previously had seen 
this species, I was yet unable to perceive a nucleus satisfac- 
torily. The narrow truncate extremities and the character- 
istic little space in each, now with one still darkish granule, 
* ‘Proceedings of the Natural History Society of Dublin,’ vol. iii, p. 83, 
ye ii, figs. 29—31; also ‘ Quarterly Journal of Microscopical Science, N.S., 
ol. IL, Pl. XII, figs. 29—31. 
VOL. VII.—NEW SER. oO 
