ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 81 



meant bj a derived function ; it is a certain type-limit, to which' tend, 

 without even sometimes quite identically attaining it, certain varying 

 intermediate forms." He enumerates seven ^distinguishing features in 

 the systematic classification of diatoms, and advocates a close comparison 

 of fossil »and living forms for determining the lines of genealogical 

 descent. Certain observations are made on the structure of the genus 

 Cymlella^ and of the various intermediate forms lying between N. 

 momnouthiana and C. microcephala. The tendency in some of the 

 intermediate forms to triundulate margins may perhaps be regarded as 

 a transitional rather than as a specific character. Descriptions of the 

 various recognized species are given, and the various changes along the 

 road of transition are pointed out. E. S. G. 



* 

 Amphora inflexa, a Rare British Diatom. — G. West {Journ. 

 Quek. Micr. Club, 1919, 14, 6 pp. 1 pi.). An authoritative reply to the 

 various doubts and queries concerning the identity of a species of diatom 

 collected by Capt. D. Griffiths in Carmarthen Bay in 1915. Amphora 

 inflexa has been published under various synonyms. It has been 

 recorded from Calvados and Biarritz in France, and from the Adriatic ; 

 in England from Ilfracombe and the Tay, previous to Capt. Griffiths' 

 find in Wales. In the present paper the differences between this species 

 and the various genera in which it has been placed are pointed out, and 

 the species itself is for the first time adequately described and figured. 

 It is a free marine diatom, living amongst the muddy sediment in rock 

 pools within tidal influence. Navicula scopulorum Breb., N. {Schizo- 

 nema) ramosissima Ag. and Toxonidia insignis Donk. were found in the 

 same gathering as Amphora inflexa (Breb.) H. L. Smith. E. S. G. 



Action of Sulphate of Copper on Plankton. — A. Betant (C. R. 

 Soc. Phys. d'Hist Nat. Geneve, 1918, 35, 86-91). A successful 

 attempt to eliminiate plankton from the drinking water taken from the 

 Lake of Geneva by the action of sulphate of copper. The annual 

 report of the Water Board shows a fairly even quantitative distribution 

 throughout the years, with the exception of May to July, when a very 

 variable increase may take place. In 1914 and 1917 it did not exceed 

 380 and 500 mm.^ per 100 litres of water, while in 1915 it reached 

 5273 mm.3, and in 1918, 3100 mm.^ per 100 litres. During the rest 

 of the year the proportion is fairly constant at 100 mm.^. Among the 

 diatoms the characteristic species are : Fragilaria crotonensis, Cyclotella, 

 Synedra, and others less frequently; among green algae, Spirogyra, 

 Sphaerocystis, etc. The method of killing the organisms with sulphate 

 of copper and letting them sink down and form a sediment is fully 

 described, and was attended with perfect success. While the natural 

 water before treatment contained 150 mm.^ of plankton, it showed only 

 7 mm.^ per 100 litres afterwards. E. S. G. 



Synopsis of the Biological Examination of Water. — J. Wilhelmi 

 (Siizungsber. Ges. naturf. Freunde Berlin, 1916, 9, 297-306 ; see also 

 Bot. Centralbl., 1917, 135, 191-92.) A criticism of the Kolkwitz- 

 Marsson scheme for the grouping of the biological contents of water, 



G 



