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NOTICES OF SERIALS. 
Quarterly Journal of Microscopical Science. No. 9. October, 1854. 
Price 4s. With Woodcuts and Lithographic Illustrations. London: S. Highley, 
22, Fleet-street. 
No. 9, October :—Original communications—(J. Gorham) On the Enlargement 
and Multiplication of the Images of the Objects, when viewed by the light admitted 
through small apertures, and on theDiascope, a new Optical Instrument—continued 
from vol. ii., page 234 ; (F. Currey) On the Spiral Threads of the Genus Trichia ; 
(G. J. Allman, M.D.,F.R.S.) Observations on Aphanizomenon flos-aquas, and a 
species of Peridinea. The former of these is a very minute alga, which appeared 
in great abundance in the large pond of the Zoological Gardens, in Phoenix Park, 
Dublin. The best account we have hitherto had of this little plant is by Mr. Ralfs, 
in his paper in the a Annals and Magazine of Natural History,” on theNostochinese; 
but, as he describes it from the dried specimens, many important facts have escaped 
his notice, which are amply recorded in this paper by Professor Allman. We have 
also an account of a new species of Peridinea, which we annex—“ During the last 
three weeks, a spectator on the banks of the large ponds in the Park must have 
been struck by a brown colour assumed by the water. This colour was sometimes 
uniformly diffused through the water ; at other times it appeared as dense clouds, 
varying from a few square yards to upwards of 100 in extent. A microscopic ex¬ 
amination of the water proved the brown colour to be entirely due to the presence 
of a minute organism, which, though it does not exactly agree with any published 
generic description, I have thought it better, by slightly modifying the genus 
Peridinea , as characterized by Ehrenberg, to place it in that genus rather than 
construct for it a new one. It varies from the 1-1000th to the 1-500th of an 
inch in diameter, and approaches in form to a sphere, divided by a deep an¬ 
nular furrow into two hemispheres, on one of which is situated another furrow, 
springing vertically from the annular furrow, and terminating at the pole. The 
organism under consideration may be regarded as essentially a solitary cell; it 
encloses reddish-brown granular contents, and a large, well-defined, central nucleus. 
In the midst of the contents are numerous clear spaces, of various sizes, which, 
however, appear to be oil-drops rather than true vacuolae. In most instances, a 
deeper-coloured ocelliform spot was evident near the polar extremity of the vertical 
furrow. It is eminently locomotive, swimming with great activity by the aid of a 
flagelliform appendage, which springs from the vertical furrow near the point of 
junction with the other, and of very minute vibratile cilia, which seem distributed 
ov6£ the surface, and not confined to the furrows, as maintained by Ehrenberg, in 
the species of Peridinea described by him. Before death, and also when only 
passing from a motile to a quiescent state, most likely preparatory to undergoing 
some important developmental change, the contents contract towards the centre, 
and then an external transparent and perfectly colourless 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 utricle, 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-contrac- 
tile; under pressure it is easily ruptured; and the minutely-granular contents, 
mixed with large oil-drops (?), escape upon the stage of the microscope. The 
