ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 659 



results. According to the Revue G-enerale ties Sciences for June 15, in 

 which a well-illustrated account of his experiments appears, on focusing 

 the instrument on the electrolyte when no current is passing, the observer 

 sees many luminous points which appear to be executing the Brownian 

 movements. On the closing of the circuit, these luminous points string 

 themselves out into a chain, which progresses towards the negative 

 electrode ; • and on reversing the current, the direction of the stream is 

 also reversed. Kossogonoff does not go so far as to assert that these 

 luminous points are the actual ions, although he shows, by reference to 

 certain calculations of Kohlrausch, that they probably have about the 

 same velocity ; but he suggests that, if they are not the ions themselves, 

 they are at least groups of ions, and this may be provisionally accepted. 

 A control experiment, in which the stream of luminous points was exposed 

 to a magnetic field at right angles to its normal direction, seemed to show 

 a dark place near the cathode such as occurs in a Geissler tube in similar 

 circumstances, followed by a layer in which the luminous points are 

 extremely numerous ; and the use of sulphate of copper as the electrolyte 

 is said to produce some very beautiful effects. This method of investiga- 

 tion seems capable of extension, and should produce further notable 

 results. 



Zschokke, W. — Anschauliche Darstellung der Entstehung und Hebung der 

 spharichen und astigmatischen Bilder. 



Deutsche Median. ZciL, Heft 9, 10 (1910) pp. 81-7, 93-7 (17 figs.). 



(6) Miscellaneous. 



Diagnosis of Natural and Artificial Silks.* — A. Herzog's mono- 

 graph is a practical introduction to the methods for determining the 

 nature of fabrics, known to the textile trade as silk, by microscopical 

 and chemical means. The booklet is divided into four parts, which deal 

 respectively with the microscopical examination of the fibres ; chemical 

 tests, in which are included the most important micro- and macro-chemical 

 reactions ; optical examination, which deals with the behaviour of the 

 fibres to polarized light and with refrangibility ; while the fourth part 

 is concerned with their ultra-microscopic appearances. Two useful tables 

 are given, one for determining the nature of silks by optical means, the 

 other by microscopico-chemical procedure. 



B. Technique. t 

 Cl) Collecting Objects, including' Culture Processes. 



Observations on a New Gregarine, Metamera schubergi g. et 

 sp. n.J — H. L. Duke obtained his material, Glossosiphonia complanata 

 Linn., a leech which serves as host to Metamera schubergi, from water in 

 the neighbourhood of Heidelberg. The leeches can be kept for an in- 



* Dresden: Theodore Steinkopff (1910) 78 pp. (50 figs.). 



t This subdivision contains (1) Collecting Objects, including Culture Pro- 

 cesses ; (2) Preparing Objects ; (3) Cutting, including Imbedding and Microtomes ; 

 (4) Staining and Injecting ; (5) Mounting, including slides, preservative fluids, etc.; 

 (6) Miscellaneous. 



X Quart. Journ. Micr. Sci., lv. (1910) pp. 261-86 (2 pis.). 



