ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 375 



glass preparations were set aside until they had become thoroughly air- 

 dry, and were then fixed in the usual way by passing through a flame. 



The dried and fixed preparation on the cover-glass was next flooded 

 with a tannate of iron mordant, and heated till the mordant steamed, 

 when the latter was removed by washing in distilled water. After 

 drying, the mordanting process was repeated, and finally the preparation 

 was stained with Ziehl fuchsin solution.* 



The photographs were taken by means of a Powell and Lealand V-r m - 

 apochromatic 1*43 N.A. and No. 10 compensating eye-piece. Messrs. 

 Powell and Lealand's apochromatic condenser was used together with 

 Gifford's light screen, the latter more particularly to absorb some of 

 the heat-rays from the condensed beam of the limelight employed, 

 before they reached the condenser. By means of this arrangement the 

 photographs were obtained with an exposure of three, minutes. The 

 magnifications are approximately equal to 2500 and 5000 diameters 

 respectively. 



With regard to the question of employing high magnifications, it 

 may be of interest to point out that in the print taken with only 2500 

 diameters magnification, the appearance in one case is such that it might 

 easily be assumed that the fiagella were bifurcated, and at first this was 

 taken to be the case, but the higher magnification clearly shows that 

 this appearance is due merely to juxtaposition of the bent middle 

 portion of a detached fiagellum, with the terminal of an attached 

 flagellum. 



The fact that the fiagella seem to reach their maximum growth in from 

 12 to 20 hours and then are soon lost, combined with their number and 

 character, suggests the possibility that they are used in the manner of 

 tentacles for attachment until certain functions are discharged, where- 

 upon the fiagella cease to be required, and are lost. 



Quantitative Estimation of the Bacillus Coli in Drinking Water.f 

 A. Gautie considers that it is not the mere presence of B. coll, but its 

 abundance or rarity that should be regarded as an index of the fffical 

 contamination of drinking water ; a great increase in the number of 

 this microbe in a water that usually contains only a small number, is of 

 •equal importance with the sudden appearance of this organism in a water 

 in which it never existed previously. For this quantitative analysis he 

 employs the method of Pere, which consists in the addition to the 

 suspected water of a small quantity of pepton broth and a known 

 proportion of carbolic acid. He gives details of the technique carried 

 out by Pere ; this he modifies in practice, by working not only with 

 100 c.cm. of water, but with decreasing amounts from 100 c.cm. to 1 drop, 

 adding always proportionate amounts of carbolic acid. 



Rothberger's Neutral Red Reaction.^ — Otto Heller describes Roth- 

 berger's neutral red reaction which is used as a differential diagnosis 

 between B. typhosus and B. coli. He refers to the several modifications 



* Fuchsin solution : 5 p.c. solution of phenol in water. To this add 1 grm. 

 fuchsin and shake well, and add slowly, drop by drop, 10 c.cm. absolute alcohol, 

 t Ann. Inst. Pasteur, xix. 1905) p. 124. 

 X Lentralbl. Bakt., Orig., 1* Abt, xxxviii.(iyOo) p. 117. 



