CURRKEY, ON FRESH-WATER ALG. 213 
this stem is very short, in comparison with the length of the 
cell which it supports, and might easily be concealed by the 
body to which the Sciadium was attached. Sciadium arbuscula 
forms an interesting addition to our British fresh-water Algee. 
4. Pandorina Morum, Ehr.—-This plant was described, with 
some other Confervoid Alge, by Mr. Henfrey, in the fourth 
volume of the ‘Transactions of the Microscopical Society.’ 
It had been previously seen by Mr. Shadbolt, and probably by 
many other observers; but, notwithstanding Mr. Shadbolt’s 
remarks in his presidential address for 1856, it is clear that 
Mr. Henfrey was right in describing it as new to England, 
the test of novelty being, not whether it had been previously 
seen, but whether it had been published as a British Alga. 
In speaking of the reproduction of Pandorina, Mr. Henfrey 
mentions two processes—1, the conversion of each gonidium 
into a new frond within the parent mass; and 2,.the conver- 
sion of the gonidia into encysted resting spores, which are 
set free, and subsequently germinate to produce new fronds. 
Upon this I may remark, that the process of becoming 
encysted does not invariably take place within the parent 
frond, for I have seen the gonidia of Pandorma escape from 
the parent frond in the form of membraneless active zoo- 
spores ; and although I was not fortunate enough to trace the 
subsequent fate of these zoospores, the probability is that, like 
those of Chlamydococcus and Gonium, they would become 
encysted at a subsequent period, as without undergoing this 
process it is difficult to see how they could produce new 
fronds. This mode of escape of the zoospores seems to throw 
some doubt upon the suggestion of Mr. Henfrey, with re- 
gard to the nature of the frond of Pandorina, which he con- 
siders to be solid, inasmuch as it does not give way or be- 
come indented by pressure, as is the case with the hollow 
frond of Volvox. If, however, the frond were sold, the 
zoospores could not well escape except by its gradual dis- 
solution, but, in the instance I have mentioned the escape 
certainly took place by a rupture (as may often be seen 
with Volvox), and not by a gradual process of dissolu- 
tion. In a paper on some Volvocinee, by Dr. Fresenius, in 
the second volume of the Transactions of the Senckenberg 
Natural History Society, he speaks of the easy escape of 
the cells of Goniwm pectorale, as bemg evidence against 
the existence in that Alga of any firm covering, and he 
draws a distinction in this respect between Gonium and 
Pandorima. My observation, however, leads me to think 
that Pandorina, as far as relates to its coat, does not sub- 
stantially differ from Volvox and Gonium. Besides the na- 
