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 Suwrrirella 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 (0-017), 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. Row ey. 
LITERATURE REFERRED TO 
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Biitschli, 0.— ‘‘ Mitteilungen iiber die Bewegung der Diatomeen.” Verhandl. Natur- 
hist.-med. Vereins Heidelberg. N.¥. Bd. iv., 5 Heft (1891). 
Dippel, L.—‘‘ Beitrage zur Kenntnis der in den Soolwissern von Kreuznach lebenden 
Diatomeen, sowie iiber Structur, Wachstum und Bewegung der Diatomeen iiber- 
haupt.” Kreuznach, Voigtlander. 1870. 
Engelmann, Th. W.—‘‘ Uber die Bewegungen der Oscillarien und Diatomeen.” Botan. 
Zeitung. 37 Jahrg. (1879), p. 49. 
Flégel.—‘‘ 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.” Mittetl. naturwiss. Vereines New-Vorpommern 
u. Rigen. Jahrg. xxvii. (1895). 
Lauterborn, R.—‘‘ Zur Frage nach der Ortsbewegung der Diatomeen.” er. Deutschen 
Bot. Gesellschaft. Bd. xii. (1894), p. 73. 
——— ‘‘Untersuchungen iiber Bau, Kernteilung und Bewegung der Diatomeen.” Aus 
dem Zoologischen Institut der Universitit Heidelberg. 1896. 
Mereschkowsky, C.—‘‘ Beobachtungen iiber die Bewegungen der Diatomaceen und ihre 
Ursache.” Botan. Zeitung. 38 Jahrg. (1880), pp. 529-540. 
Miller, 0.—‘‘ Durchbrechungen der Zellwand in ihren Beziehungen zur Ortsbewegung 
der Bacillariaceen.” Ber. Deutsch. Bot. Gesellschaft. Bd. vil., Heft 4 (1889), 
pp. 169-180. 
—_—— ‘Die Ortsbewegung der Bacillariaceen betreffend.” Op. cit. Bd. xi, (1893), 
p. 571. Bad, xii. (1894), pp. 136-143. Bd. xiv. (1896), pp. 54-64, 111-128, 
Pfitzer, E.—‘‘ Untersuchungen 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. 
Zeitschr. wiss. Zool. Bad. lviii. (1894), p. 340. 
Schultze, M.—‘‘ Die Bewegung der Diatomeen.” Archiv. mikroskop. Anat. Bad, i. 
(1865), p. 374. 
Siebold, C. Th. v.—‘‘ Uber einzellige Pflanzen und Tiere.” Zeitschr. wiss. Zool. -Bd. i. 
(1849), p. 270. 
