ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 605 



Collecting- and Rearing- Volvox.* — G. R. La Rue collected Volvox 

 ill the ;iutnmn of 1915, and in the spring of 191(1 found they had 

 multiplied freely. He gives certain cautions — e.g. the water for the 

 cultures should lie from the same source as the organisms. Tap-water 

 for making up the culture or for making good evaporation should never 

 be used. Keep the cultures covered to prevent evaporation and con- 

 sequent change in density of the medium, and to exchide dust and 

 bacteria. The presence of organic material seems to be beneficial. 

 Direct sunlight is unnecessary and is to be avoided, because it causes 

 too great variations in temperature in closed vessels. North light is 

 good ; in fact many algte thrive in it. Low temperature, above 

 freezing, seems to favour development. Old cultures, unless hopelessly 

 foul, should be kept, and the organisms given a chance to reappear. 



New Solid Medium for the Isolation of the Cholera Vibrio.f — 

 H. Gr. Gibson gives the following formula for the preparation of this 

 medium : Agar, 3 grm. ; pepton, 10 grm. ; starch, 10 grm. ; sodium 

 bicarb., 1 • 5 grm. : litmus (sufficient to colour medium) ; water, 1000 

 c.cm. AVeigh out 30 grm. of powdered agar and emulsify with 250 c.cm. 

 of cold water. Then weigh out 10 grm. of pepton and 1 • 5 grm. of 

 sodium bicarb. Mix together and emulsify in another 250 c.cm. of 

 cold water. The two emulsions are then mixed in a two-litre flask 

 and 500 c.cm. of water added. The solution is completed in a 

 steamer. When dissolved the medium is clarified with white of egg 

 and filtered in the steamer. Weigh out 10 grm. of potato starch, 

 emulsify it with some of the filtered agar, and add the emulsion to the 

 remainder of the medium. The whole is sterilized by the fractional 

 method, after which enough sterile aqueous solution of litmus is added 

 to bring about a blue colour of the medium. The final reaction of the 

 medium should be : 2 to phenolphthalcin ; 0'15 p.c. sodium bicarb, 

 gave the best results. 



Examination of the plates eighteen hours after inoculation showed 

 the cholera colonies to be pink, the other colonies to be blue or whitish. 

 In twenty-four to twenty-six hours the cholera colonies are pink, with 

 a faint pink halo. In forty-eight hours other colonies may be pink, 

 but the cholera colonies may l)e distinguished by their red centres 

 which the other colonies lack. The only other organisms which are 

 known to acidify starch are some of the diphtheroia group and some of 

 the non-pathogenic water vibrios. Gram's stain and the serological 

 test dispose of these organisms. 



Acidification of Culture Media by Alkaline Salts. | — L. Bourdet 

 has investigated the question of the acidification of culture media by 

 means of their contained alkaline salts during sterilization in the auto- 

 clave. The acidification is produced by action of certain salts upon 

 sugars and peptons contained in the different media : for example, the 



* Trans. Amer. Micr. Soc, xxxv. (1916) pp. 150-1. 

 t Brit. Med. Jonrn., Sept. 30. 1916, pp. 454-5. 

 : C.R. Soc. Biol. Paris, Ixxix. (1916) pp. 665-8. 



