44 
attained, but the difficulties increase with the length of the 
tube. It has, however, occurred to me that by centrifugal 
force the limit may be reached in tubes a few inches long, 
and I am at present preparing some experiments for this 
purpose, of which I hope soon to be able to give some 
account. 
MICROSCOPICAL AND NATURAL HISTORY SECTION. 
October 11th, 1880. 
Alfred Brothers, F.R.A.S., in the Chair. 
On some Entomostraca, &c., found in Derwentwater in 
September, 1879,” by Mr. John Boyd. 
A new Locality for Leptodora Hyalina. 
“Quite a little excitement was caused in August last year 
by the announcement of the discovery of Leptodora Hyalina, 
for the first time in England, in the Olton Reservoir. The 
last fortnight in September I spent at Keswick, and from 
the description of the places in which it has previously been 
found here and on the Continent, I thought it very likely 
that it might be obtained also from Lake Derwentwater ; 
I therefore constructed a net of fine muslin, about two feet 
long, gradually tapering to an aperture at the end; in this 
aperture I inserted the neck of a wide-mouthed bottle; this 
apparatus was slowly towed after a boat. The water passed 
through the net, leaving all the animalcules in the bottle, 
and to my delight almost the first haul brought up several 
specimens of Leptodora; afterwards I got them more plenti- 
fully, but found that in some parts of the lake the bottle 
brought none up. They need to be looked for very carefully, 
for they are so exceedingly transparent that one very easily 
