ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 91 



cell, that the chlorophyll-bands increase in length, not exclusively by 

 apical, but also by intercalary growth. Since the growth of the bands 

 takes place in the direction of the coils, and therefore obliquely to the 

 surface of the cell-wall, tbere must be a gliding motion of the bands 

 through the parietal protoplasm. To facilitate this movement, the 

 bands have hollow channels, in order to make the gliding surface as 

 small as possible. But, since the bands have a marked tendency to> 

 contraction, they are provided with vertical books which prevent the 

 bands from becoming altogether detached from the parietal protoplasm. 



Asterionella as a Cause of Foulness in Drinking Water.* — Mr. 

 G. C. Whipple and Mr. D. D. Jackson have studied the biology of 

 Asterionella formosa, a diatom which is a frequent cause of foulness in 

 drinking water in Amerio, giving to it a fishy or geranium-like odour, 

 caused by the formation of an oil analogous to the essential oils. The 

 diatom forms spores during periods of stagnation at the bottom of 

 reservoirs, and increases with very great rapidity when these spores 

 germinate, this growth taking place chiefly during the spring and 

 autumn. The growth of the diatom is greatly favoured by light ; and 

 the best mode of preventing its increase is by storing the water in the 

 dark. 



Marine Diatoms of France, j — MM. H. and M. Peragallo have 

 issued the first part of an important contribution to diatomic literature, 

 an account of the marine diatoms of Fiance. The Diatoinaceae are 

 divided into three sections, — Raphideee, Pseud o-raphideae, and Anara- 

 phideae. The Raphideae consist of three tribes, the HeteroiJae, Navi- 

 culoidae, and Tropidoi'dae. The Heteroi'dae are characterised as having 

 frustules with two unequal valves, the lower valve generally concave, 

 having only one raphe and row of nodules, and comprise the single family 

 Achnantheae, and the 6 genera, Cyclophora (1 sp.), Achnanthes (10 sp.), 

 Cvcconeis (20 sp.), Rhoicosphsenia (1 sp.), Anorthoneis (1 sp.), and Cam- 

 pyloneis (1 sp.). The Naviculoidae have frustules composed of equal 

 valves, neither winged nor keeled, and are arranged in five groups, viz. : 

 — the Mastigogloiete, Naviculese, Pleurosigmeas, Gomphoneineae, and 

 Cymbelleae. The Naviculeae include the 7 penera Dictyoneis (2 sp.),. 

 Mastoneis (1 sp.), Cistula (1 sp.), Stenoneis (1 sp.), Berkeleya (2 sp.), 

 Brebissonia (1 sp.), and Navicula, the very numerous species of which 

 are divided into 9 sections and 28 groups. The Pleurosigmeae consist 

 of 4 genera : — Pleurosigma (46 sp.), Bhoicosigma (7 sp.), Donkinia 

 (3 sp.), and Toxonidea (3 sp.). The Tropidoideae (Aniphitropidea3) 

 are made up of 3 genera, Amphiprora (4 sp.), Tropidcneis (6 sp.), and 

 Auricula (7 sp.). A commencement of the Cymbelleae is made with its 

 two genera Amphora and Cymbella. The present part is illustrated by 

 fifty beautiful plates. 



Diatoms in Basalt.:]: — Dr. A. M. Edwards records the discovery of 

 valves of diatoms in the trap-rock of New Jersey, possibly the oldest 

 record. Forms belonging to Synedra and Meloseira were readily dis- 

 tinguished. 



* Journ. N. England Waterworks Asa., xiv. (1899) 25 pp., 2 pis. and 1 chart, 

 t ' Les Di;itonie'es marines de France,' l ie partie, Paris, 236 pp. and 50 p\s. 4 

 X Amer. Mon. Micr. Journ., xx. (1899) pp. 292-4. 



