101 
Dr. Alcock also exhibited a lingual riband of the Patella 
athletica, from Bray, in Ireland ; he compared it with that 
of the common limpet, Patella vulgata, and pointed out the 
differences in the form of the teeth. 
Dr. Roberts exhibited some mounted specimens of blood- 
corpuscles from an albuminous urine, which showed an 
appearance as if the contents of the cells had separated from 
the cell-Avall, and become aggregated round the centre like a 
nucleus. When these corpuscles were treated with magenta, 
the central portion was either not coloured at all, or only 
faintly so, whereas the circumferential portions became deeply 
tinted. By treating fresh blood with an excess of a solution 
of carbolic acid this appearance could he produced at will. In 
the blood-corpuscles of the fowl a similar effect was produced 
by the carbolic acid solution ; the cell contents appeared 
to detach themselves from the cell-wall and to collect round 
the nucleus. The appearances presented, strongly suggested 
the idea that the cell envelope of the blood-disc was a double 
membrane ; that the inner separated under certain circum- 
stances from the outer membrane and shrank in toward the 
centre. Dr. Hensen, of Kiel,* seems to have convinced him- 
self that such is the case in the blood -disc of the frog, and he 
compares the inner membrane to the primordial utricle of 
the vegetable cell. Of the prolongations described by Dr. 
Hensen as stretching radially between the shrunk inner 
membrane and the outer one, Dr. Roberts saw nothing. If 
the said view of the structure of the blood-cells were sub- 
stantiated, it would greatly facilitate the explanation produced 
on these cells by magenta and tannin. 
Mr. Charles O’Neill, F.C.S., exhibited a mounted fibre of 
Orleans cotton, torn by a gradually increasing weight sus- 
pended to its extremity. It had sustained a weight (gradually 
* Siebold and Kolliker’s Zeitsclirift, for 1861, p. 263. 
