192 PROCEEDINGS OF SOCIETIES. 
together into indefinitely long chains by a cylindrical mucous 
. investment, comparable to that of Hormospora mutabilis (Bréb.), 
fresh specimens of which latter he was also fortunately able to 
lay on the table. He had never seen this Spirotenia, nor, indeed, 
any of the other species of that genus presenting this condition. 
When he first took this very well-marked and very minute species 
there were never more than two cells, as is usual in the genus, 
held together by a mucous coating, which two cells usually be- 
come disassociated before the next ensuing self-division of either 
cell takes place. Though thus held together, the so-connected 
chain could not, strictly speaking, be called a filament, as the 
cells themselves did not remain united, but were, indeed, often 
separated by a perceptible interval, thus unlike such forms as 
Hyalotheca, Sphzrozosma, &c. With some, indeed, a question 
might arise as to the advisability of holding filamentous genera 
in Desmidieew as distinct per se from free genera. Thus, as 
regards Diatomacee, Heiberg has already propounded the view 
that distinctions founded on the external conditions, or on 
the mode in which the cells are held more or less definitely 
together, in filaments or otherwise, should not be regarded as of 
generic value. And, as regards Desmidia, in this point of view, 
Dr. Wallich finds a filamentous Docidium and a filamentous 
Micrasterias in Bengal; but, on the other hand, while Des- 
midium might, perhaps, be regarded as representing a fila- 
mentous Staurastrum, Spherozosma a filamentous Cosmarium, 
Hyalotheca also a filamentous Cosmarium or Euastrum, yet cer- 
tain of these seem formed to exist as filamentous types (such as 
Spherozosma, Aptogonum, and some Bengal forms), by reason of 
the connecting processes between the links forming fulcra of 
attachment. But, of course, in the Spirotenia now shown there 
were no uniting processes ; as already said, the only bond of union 
being the tubular mucous investment. As the cells themselves 
showed no distinction whatever from the form already described, 
there could be no doubt but that this was S. parvula, and a beauti- 
fully distinct and constant form. Like most, it must be examined 
fresh to see its characters, with the parietal band of endochrome 
of one or two turns. 
Mr. Crowe showed Cosmarium curtum (Ralfs) = Penium curtum 
(Bréb.) taken from a shallow rut in the avenue before his own 
door at Bray. The first occasion he had taken it was on a visit. 
to North Wales. He had watched it for some time in its present 
locality, but had not found it conjugating. 
Mr. Archer remarked that probably this well-marked form 
might turn out to be more common than we had supposed, as 
this situation agreed so much in character with that in which he 
had himself found it close to the “ Dargle” gate, and which is 
unlike that in which Desmidiew are usually found. Unfortu- 
nately for a protracted observation of this species as to its conju- 
gating state, it seems to have occurred only in pools which are 
