132 HUTTON, ON ARACHNOIDISCUS. 
of the primordial cells to put them forth. Nor, again, when 
present, do they all seem to reach the inner surface of the 
envelope-cell, and some even finely drawn out appear to 
project obliquely inwardly. Similar extensions of the pro- 
toplasm are, in other stages of development of Stephano- 
sphera, to be seen figured in Cohn and Wichura’s memoir,* 
which in the course of development are again drawn in; so 
also in Chlamydococcus. Now, it seems to me that this 
ordinary behaviour of the primordial cells in the develop- 
ment of this organism, and the action of my rapidly reptant 
ameceboid bodies (precisely the same primordial cells), are 
manifestations of one and the same phenomenon, differing only 
in the degree of intensity with which they are evinced. 
(To be continued.) 
On the Discovery of ARACHNOIDIscUS oRNaATUS and A. 
Exrensercil, at Matanipe, Co. Dusiin. By Captain 
F. W. Hurron, F.G.S., Deputy-Assistant-Quartermaster- 
General at Dublin. 
On the 14th December, 1864, I made a gathering of 
diatoms at Malahide, from a small pool of brackish water 
near the sea, and west of the railway ; the pool was apparently 
above the reach of the highest tides, but the water in it was 
very salt. On the 16th I boiled 
a small portion of this gathering 
im nitric acid, and dried it on a slide 
for examination, and amongst the 
other diatoms I was surprised to 
find a beautiful specimen of Arach- 
noidiscus ornatus. (See fig.) 
I then carefully examined the rest 
of the gathering, but could only 
detect one specimen of A. Hhren- 
berg init. The other diatoms in 
this gathering were Epithemia 
musculus, Cocconeis  scutellum, 
Coscinodiscus radiatus, Actino- 
cyclus undulatus, Surirella gem- 
ma, S. salina, Nitzschia sigma, 
N. dubia, Amphiprora alata, Na- 
vicula didyma, Pinnularia cypri- 
nus, Pleurosigma strigosum, P. angulatum, P. acuminatum, P. 
* * Ueber Stephanosphera,’ tab. B, 12, a, d, c. 
