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Mr. J. Ralfs on the mode of growth in Oscillatoria. 39 
in Stephens’s collection ; the descriptions in his works however are 
not taken from these specimens, but borrowed from Denny. 
-Euplectus Kirbii, Denny, of which I have examined the original 
specimen in the British Museum, is not identical with H. signatus, 
as Erichson and Aubé suppose, but with #. Fischeri, Aubé (Tischer, 
Heer). Denny has overlooked the pit in the forehead which charac- 
terizes this species. 
Stephens refers the Huplectus sanguineus, Denny, as a synonym 
to E. minutus of Marsham, but incorrectly; the specimen of the latter 
differs in nothing from an ordinary £. signatus. 
E. ruficornis, Ste., is synonymous with #. ambiguus, Reichb. 
Bythinus grandipalpus, Ste., is the female of B. Curtisiz, Denny. 
Bryazis assimilis, Curt., I have not seen. 
The specimen named Bryavis insignis, Reichb., in Stephens’s 
collection, does not agree at all with the true P. insignis, Reichb. 
(=Tyrus mucronatus), but is the same insect as Bryaxis juncorum. 
V1.—On the mode of growth in Oscillatoria and allied genera. 
By Joun Ratrrs, M.R.C.S., Penzance*. 
Tue growth of the lower Algz by repeated transverse division of 
their cells is now a well-established fact. In the Desmidiee and 
the Palmellee this division is usually complete and gives rise to 
distinct individuals. In the latter family the common gelatinous 
matrix mostly retains them in such close connection that the 
entire mass is regarded as a frond, of which the cells are only 
portions. ‘The case is essentially similar in the Desmidiee ; but 
in them the common matrix is so exceedingly thin that it can 
scarcely be detected, whilst the slightest touch scatters the cells, 
rendering their independence apparent, and hence each individual 
is considered a frond. 
In Tiresias and many other simple, filamentous Algz, the 
divided cells remain closely united, and form a jointed filament 
which continues to elongate until the cells cease to divide. 
I believe that in Oscillatoria we may trace a mode of growth 
of an intermediate kind and connecting these extremes. In many 
species of this genus the stratum spreads with great rapidity. 
This rapid growth cannot be caused by zoospores or granules 
vegetating in constant succession, because, although the fila- 
ments vary in length, their breadth is uniform. It does not de- 
pend on the simple elongation of the filaments, because, in many 
species, the filaments always remain short, notwithstanding the 
eat increase of the mass. 
The difficulty of tracing the growth in Oscillatoria is enhanced 
by its cells bemg frequently confluent, or having their divisions 
* Read before the Botanical Society of Edinburgh, December 14, 1848. 
