ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
343 
able evils, the authors, while acknowledging the difficulty of obtaining 
pure cultivations, do not seem to consider this as impossible. From 
faeces were obtained cultures of A. coli, A. guttula , A. spinosa ; from 
Blatta-ex crement, A . blattarum ; from muddy water, A. guttula , nodosa , 
diffluens, arborescens, gracilis , spinosa, and oblonga ; from damp earth in 
unhealthy places, A. guttula, spinosa, and arborescens ; from beer yeast, 
A. guttula and spinosa. 
Culture Medium for Algse and Amoeba.* — Dr. N. Tischutkin recom- 
mends 1 percent, aqueous solution of agar for the cultivation both of 
Algae and of Amoebae. 
Crystal Formation in Culture Media. -j* — Dr. Marion Dorset regards 
the early formation of crystals in freshly prepared agar as a special 
characteristic of Bacillus pyocyaneus. Other bacteria produce crystals in 
culture media, but only when the media are old, and therefore partially 
dried. 
(2) Preparing- Objects. 
Methods for Demonstrating the Continuity of Protoplasm.} — In 
discussing the various methods adopted for demonstrating the continuity 
of protoplasm, Herr A. Meyer first makes a few remarks on fixation Of 
the tissue. For this 1 per cent, osmic acid is recommended, though 
strong iodopotassic iodide (iodine 3, iodide of potassium 3, water 20) and 
potassium-bismuth iodide solutions give favourable results. For soften- 
ing membranes sulphuric acid is the best agent (H 2 S0 4 1 vol. to O’ 5-3 
vols. water). A very strong solution of iodine made by dissolving 1 vol. 
of iodine and 1 of iodide of potassium in a few drops of water, and then 
adding 200 ccm. of water, is useful occasionally for staining the threads 
of protoplasm. By staining with Hoffmann’s blue or Bavarian blue, the 
continuity of the protoplasmic processes was rendered distinctly visible. 
The sections were placed for a few minutes in a solution of 1 grm. of 
pigment and 150 grm. of 50 per cent, spirit, and examined in glycerin. 
Permanent preparations can be made from tissue fixed and hardened in 
osmic acid or alcohol by over-staining the sections in Delafield’s haema- 
toxylin (24 hours), and, after washing in 60 per cent, spirit, decolorising 
in 0 • 5 per cent. HOI. The sections must then be immersed in 60 per 
cent, spirit rendered alkaline by the addition of ammonia (10 drops to 
100 ccm.). After this they are transferred to absolute alcohol, xylol, 
and mounted in balsam. A method for staining after mordanting with 
iodine is described at some length. The reagents required are : — • 
(1) Iodopotassic iodide solution (iodine 1, iodide of potassium 1, water 
200) ; (2) sulphuric acid (1-3), which has been saturated with iodine by 
standing over some iodine ; (3) a solution of 1 grm. of pyoktanin 
coeruleum (Merck) in 30 ccm. of water. The sections are immersed in 
solution 1 for some minutes, and then placed on a slide and covered with 
a slip. Solutions 2 and 3 are added at the side of the cover ; and having 
been allowed to act for about three minutes, the slide, section and cover- 
glass are immersed in a large quantity of water. Having been quickly 
washed, the section is placed on a clean slide and examined in glycerin. 
* Centralbl. Bakt. u. Par., 2 te Abt., iii. (1897) pp. 183-8. 
t Op. cit., l te Abt., xxi. (1897) pp. 473-4. 
X Ber. Deutsch. Bot. Gesell., xv. (1897) pp. 166-77. 
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