ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
841 
exhibited slow movements. The protoplasm of the longer forms is 
homogeneous, and shows a few highly refracting puncta ; but these 
have nothing in common with spores. Other bacillary forms are highly 
refracting throughout, and some not at all. The oval forms, most 
frequent in agar cultivations, are homogeneous, and always refracting. 
The preparations were fixed with nitric acid after the method intro- 
duced by Sjobring, and afterwards stained in various ways ; but that 
which gave the most satisfactory results was a hydroalcoholic solution 
of safranin. The preparations were stained, without heat, in from 1-2 
minutes. Cultivations in meat broth at 37° for 3-4 days were found 
to answer best, as in these the developmental stages could be easily 
followed out. During the first period the bacilli stain deeply and regularly 
throughout, and at this stage they may attain a length of 8-9 /x. Then 
the deeply stained portion is confined to long central areas, the external 
part being pale. After this is a stage where the body is pale, but studded 
along its sides with chromophilous granules. These granules next form 
oval rings, the granules being at first quite separate, but eventually becom- 
ing a series of darkly stained loops joined at their extremities, so that a 
moniliform appearance is produced. The rest of the organism is still 
pale pink. In the next stage the oval elements begin to separate from 
one another, and are finally set free. When free they lose their oval 
form and become cylindrical. The cylinders stain deeply throughout, 
and, in fact, are but the early condition of the first stage. Thus the 
cycle is formed. 
The free oval forms are about 1*5 /x long and 0'9 broad, and while 
oval the periphery stains much more deeply than the centre. The 
authors do not consider these oval forms to be spores, as they have 
very slight resistance to heat, and they are not stained by methods 
used for spore-staining. They hold that these appearances are those of 
a real nuclear fission, having a remote resemblance to the mitosis of the 
higher cells. 
Influence of Light on Bacteria.* — Prof. H. Buchner has been 
making a series of experiments for the purpose of ascertaining to what 
extent the vitality of micro-organisms suspended in water is influenced 
by the direct action of sunlight. The organisms used for these experi- 
ments were typhoid bacilli, B. coli communis , B. pyocyaneus , cholera 
vibrio, and various putrefactive bacteria, which, in order to imitate the 
natural conditions as nearly as possible, were placed partly in sterilized 
and partly in non -sterilized water. The vessels in which the water was 
contained were of various sizes and shapes, and for each experiment the 
test was always double, that is to say, one vessel was open and exposed 
to the light, while the other was covered and protected from the influence 
of light by means of black paper. Some experiments were made indoors, 
but most in the open air ; in all cases the temperature was recorded. 
The number of germs was estimated before and after the experiment by 
means of the gelatin plate method. 
The experiments show conclusively that light exerted a powerful 
disinfecting influence upon the aforesaid bacteria when suspended in 
water. For example, water containing 100,000 germs of B. coli 
* Centralbl. f. Bakteriol. u. Parasitenk., xi. (1892) pp. 781-3. 
3 L 
1892. 
