84 THE MICROSCOPICAL NEWS. 
of trees, and thus striking an average, which will give at least 
approximate ages. ‘Trees measured in this way are found in many 
cases to be of less antiquity than was formerly supposed. The 
average age of oaks, for instance, is put down at 1,000, whilst this 
method reduces it more than one-half. 
MarinE AQuariA.—The usual ordinary weekly meeting of the 
Lower Mosley-street Natural History Society was held on Monday 
evening, Jan. 14th, when Mr. Robert Graham read a paper on the 
management of Marine Aquaria which was illustrated by practical 
demonstrations on a small aquarium brought for the purpose and 
containing a crab which had recently cast its exoskeleton, a mass 
of sea-weed, several small anemones, which were born in Mr. 
Graham’s large aquarium at home, and a young star-fish, which was 
very active during the whole of the evening. Mr. Graham, who has 
kept marine aquaria for several years, gave some valuable information 
relative to their successful management, and dwelt at length upon 
such matters as the preparation of the bottom, stocking, feeding, 
filtration and aerifying of the water, and the removal of decaying 
matter. The demonstrations were the filtering of the water by 
means of cotton-wool, removal of matter from the bottom by a 
glass tube, and feeding of the anemones with small portions of 
mussels, which were conveyed to them by a pair of wooden forceps. 
It was noticed during the latter operation that the wily crab 
pounced upon one of the anemones and deprived it of its morsel. 
In referring to anemones it was stated by the lecturer that a species 
of Actinia had been kept in an aquarium for more than twenty 
years, and during that space of time had given birth to 324 young, 
240 on one occasion being born in one night. 
MANCHESTER MicroscopicaL Society.—Axnual Soiree. The 
Annual Soiree of this Society was held in the Lecture Hall of the 
Athenzeum on Friday, Jan. 25th, when Dr. H. C. Sorby, F.R.S., 
delivered a very important address upon “The Application of 
Quantitative Methods to the Study of the Free-Swimming Minute 
Animals in Fresh and Sea Water,” showing the apparatus and 
methods used in collecting the material for examination—Small 
animals common in fresh water—Quantitative distribution of the 
minute animals in pure and impure rivers—Distribution in rivers, 
canals, ponds, &c.—Small animals, &c., common in sea water— 
Distribution in relation to the depth of the water and the state of 
the tide—Distribution in various localities at various times of the 
year—Connection between the number of the minute animals and 
the success of oyster culture, and also the distribution of certain 
common fishes—Drawings of the animals and plants, and tables of 
the results, shown as lantern slides, were shown with the oxy- 
hydrogen lamp. 
