416 NATURAL SCIENCE [December 1898 



for demonstrating the centrosome and nucleoli in specially prepared 

 material. "When stained, the specimens were passed successively through 

 35%, 70%, 95%, and absolute alcohol into oil of cloves for clearing 

 purposes, and finally mounted in dammar. The alcohol baths must 

 be changed very gradually both when fixing and staining, otherwise 

 distortions of the protoplasm are certain to occur. Isolation of 

 the nucleus in Surrirella could be accomplished by placing the 

 stained specimen in dammar under a cover-glass provided with wax 

 feet and pressing this down until the frustule began to gape. Then, 

 by gently and persistently tapping the cover-glass with a needle, the 

 nucleus could often be completely freed for examination. 



It was possible to stain the diatoms to a certain extent during life 

 in a very weak solution of methylene blue (1 in 100,000), in which 

 they would live for days. If transferred from this to a stronger so- 

 lution (0'01%), some of the cell contents were stained in a very 

 characteristic manner ; but so soon as the nucleus began to take up 

 the stain, it was a sure sign that the vitality of the cell was on the 

 wane, although the diatom might continue to move slowly for a time. 

 In no case was observation of living specimens omitted, for a whole 

 succession of phenomena could only be adequately studied in this 

 way, and such observations possess special value for checking the re- 

 sults obtained after the use of reagents. A Seibert apochromatic 

 objective of 2 mm. focal length was usually employed, in combination 

 with a No. 12 ocular, giving a magnification of about 1200. 



Town Museum, Leicester. F. R. EOWLEY. 



LITERATURE REFERRED TO 



Borscow. — "Die Siisswasser-BaciHariaceen des siidwestlichen Russlands." 1873. 

 Btitschli, O.— " Mitteilungen liber die Bewegung der Diatomeen." Verhandl. Natur- 



hist.-med. Vcreins Heidelberg. N.F. Bd. iv., 5 Heft (1891). 

 Dippel, L. — " Beitrage zur Kenntnis der in den Soolwassern von Kreuznach lebenden 



Diatomeen, sowie iiber Structur, Wacbstnm und Bewegung der Diatomeen iiber- 



haupt." Kreuznach, Voigtlander. 1870. 

 Engelmann, Th. W. — " Uber die Bewegungen der Oscillarien und Diatomeen." Botan. 



Zeilung. 37 Jahrg. (1879), p. 49. 

 Flbgel. — "Researches on the Structure of the Cell-walls of Diatoms." Journ. Roy. 



Micro. Soc. 1883. 

 Hauptfleisch, P. — "Die Auxosporenbildung von Brebissonia Boeckii Grunow." "Die 



Ortsbewegung der Bacillariaceen." Mitteil. naturiviss. Vereines Neu-Vorpommern 



u. Riigcn. Jahrg. xxvii. (1895). 

 Lauterborn. R. — " Zur Frage nach der Ortsbewegung der Diatomeen." Ber. Deutschen 



Bot. Oesellschafl. Bd. xii. (1894), p. 73. 

 ■ " Untersuclmngen iiber Ban, Kern teihvng und Bewegung der Diatomeen." Aus 



dem Zoologischen Institut der Universitat Heidelberg. 1896. 

 Mereschkowsky, C. — " Beobachtungen iiber die Bewegungen der Diatomaceen und ihre 



Ursache." Botan. Zeitung. 38 Jahrg. (1880), pp. 529-540. 

 MUUer, O. — " Durchbrechungen der Zellwand in ihren Beziehungen zur Ortsbewegung 



der Bacillariaceen." Ber. Dcutsch. Bot. Gesellseha ft. Bd. vii., Heft 4 (1889), 



pp. 169-180. 

 "Die Ortsbewegung der Bacillariaceen betreffend." Op. cit. Bd. xi. (1893), 



p. 571. Bd. xii. (1894), pp. 136-143. Bd. xiv. (1896), pp. 54-64, 111-128. 

 Pfitzer, E. — " Untersuclmngen iiber Bau und Entwickelung der Bacillariaceen (Diato- 

 maceen)." Bot. Abhandl. a. d. Gebiet d. Morpho. und Physiol, herausg. , von 



J. Hanstein. 2 Heft. Bonn, 1871. 

 Schewiakoff, W. — Uber die Ursache der fortschreitenden Bewegung der Gregarinen. 



Zeit.schr. wiss. Zool. Bd. lviii. (1894), p. 340. 

 Schultze, M. — "Die Bewegung der Diatomeen." Arcliiv. mikroskop. Anat. Bd. i. 



(1865), p. 374. 

 Siebold, C. Th. v. — " Uber einzellige Pflanzen und Tiere." Zeitschr. iriss. Zool. Bd. i. 



(1849), p. 270. 



