RLY 
It is eminently locomotive, swimming with great activity 
by the aid of a flagelliform appendage, which springs from the 
vertical furrow near the pomt of junction with the other, and 
of very minute vibratile cilia, which seem distributed over the 
surface, and not confined to the furrows, as maintained by 
Ehrenberg, in the species of Peridinee described by him. 
Before death, or, perhaps, when only passing from a mo- 
tile to a quiescent state, the contents contract towards the 
centre, and then an external transparent and perfectly co- 
lourless vesicle becomes visible, while the flagellum and cilia 
- disappear. The contracted contents present a very definite 
and generally spherical boundary, and are evidently included 
in a distinct cell; the resemblance of this internal cell to the 
primordial utrical, and that of the external investing vesicle to 
the cellulose wall of the vegetable cell, are too obvious to be 
overlooked, though the iodine and sulphuric acid test failed in 
indicating the presence of cellulose. The external investing 
vesicle is non-contractile ; under pressure it is easily ruptured, 
and the minutely granular contents, mixed with large oil- 
drops (?), escape upon the stage of the microscope. The nu- 
cleus is then easily isolated ; it is of an irregular, oval form, 
quite colourless, and marked on its surface with curved striz. 
Multiplication is effected by transverse division, which 
takes place parallel to the annular furrow, and in the unfur- 
rowed hemisphere. This process appears to be invariably 
preceded by a division of the nucleus, and the author had suc- 
ceeded in isolating nuclei, presenting almost every stage of 
transverse fission. 
Believing the species now described to be new, the author 
named it P. wberrima. 
[Since the communication of the above facts to the Aca- 
demy, the coloration of the ponds has much increased in in- 
tensity. On the 9th of July the author again visited them. 
The colour in some parts was then of so deep a brown, that a 
