12 
pinion which gears into all the selenite rings at the same time, and 
is actuated by means of a small milled head. li this milled head 
is turned round, it will be seen that all the selenites are being 
rotated at the same moment, but with unequal velocities, and by 
the aid of this ingenious contrivance it will be found that the 
most beautiful combinations of colour are produced, and will go 
on varying until the axes of the selenites return again to their 
normal position, which will of course depend upon the relation 
between the numbers of the pinion and the teeth of the selenite 
rings. Mr. Cushing illustrated his paper with carefully made 
drawings of all the polariscopes he described, and at the close 
presented to the Club a treatise, by Chas. Woodward, Esq., F.R.S., 
entitled “‘A Familiar Introduction to the Study of Polarised 
Light.” After a few remarks from the President, the unanimous 
thanks of the Club were accorded to Dr. Strong and Mr. Cushing 
for their interesting papers. 
March 15th, 1871.—Henry Lee, Esq., President, in the chair. 
The following gentlemen were balloted for and duly elected 
Members :—Mr. W. H. Beeby, Mr. J. S. Crowley, and Mr. W. 
T. Loy.—The PresipEnT presented the Club with “The Prepara- 
tion and Mounting of Microscopical Objects,” by Davies, and 
“ The Collector’s Hand-book of Alge.” He also announced that 
since the last meeting three new Microscopical Societies had been 
formed, viz. :—the Sydenham and Forest Hill, the Margate, and 
the South London Microscopical and Natural History Society. 
Mr. J. S. Jonnson, M.R.C.S., read a Paper “On a Micro- 
SCOPICAL EXAMINATION OF THE OysTER,” which he illustrated by 
numerous anatomical preparations. 
A lengthy discussion followed, during which the Presipent 
stated his belief that the Oyster did not produce more than one 
spat in a year, and although they might, from unfavourable cir- 
cumstances, be stopped from breeding during a whole season, 
they certainly would not spawn at all that year. With regard to 
the scarcity of oysters, it was caused by atmospheric and climatic 
influences, which it was impossible to account for. Oysters bred 
just as freely as ever they did, but the young ones did not adhere, 
and that was why we felt the loss. At Herne Bay, in June, the year 
before last, the sea was so thickly impregnated with young oysters 
in their swimming condition that a great number might be taken 
up by merely dipping the blade of a knife into the water. During 
that month the nights were very cold, and, believing that a low 
temperature, among other things, prevented the development of the 
fry, he and Mr. Frank Buckland deposited some of them in a vase 
of sea-water. On reducing the temperature by inserting a piece of 
ice, he found that the young oysters sank to the bottom of the 
vessel, but on withdrawing the ice, and restoring the water to its 
