252 Dr. Greville on some British Diatomacese. June 29th, one east skin was removed. July 4 th, one „ „ „ 9th, one „ „ „ 11th, one „ „ At this date four individuals were given to a friend, so that the number was reduced to four. July 1 5th, one cast skin was removed. „ 17th, one „ „ „ 18th, one „ „ „ 21st, one „ „ „ 30th, one „ „ August 3rd, one „ „ „ 4th, two „ ,, „ 12th, one of the prawns died during the moulting. „ 14th, one cast skin was removed from the aquarium. „ 21st, one „ „ „ September 2nd, one „ „ „ So that the period appears to vary from twelve to twenty-four days. This variation may depend upon the quantity of food taken by the respective individuals, and also on the varying temperature of the aquarium, which, from its small capacity and other circumstances, is very liable to be readily affected by the heat of the sun through the day, and the effects of radiation during a clear night. I may mention that if these cast skins are not removed from the water, the prawns will devour all the smaller and softer parts, as the legs, the palpi, and the false or swimming feet, with great rapidity. I hope in a future communication to add several observations on other varieties of the PalcemonidcB. » Apothecaries' Hall, Blackfriars, March 12, 1855. XXIII. — Report on a Collection of Diatomacese made in the District of Braemar by Professor Balfour and Mr. George Lawson. By R. K. Greville, LL.D. &c.* [With a Plate.] In the course of the autumn of last year. Professor Balfour made a botanical excursion with a small party of friends and pupils to the mountainous district of Braemar ; and his attention having been directed for some time past to the Diatomacese, he, and Mr. George Lawson made a considerable number of gatherings in a great variety of situations, from the patches of snow which even in summer are always to be found in certain nooks and * Read before the Botanical Society of Edinburgh, Feb. 8, 1855.
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