ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 493 



mentation in saccharine fluids, and its develoj)ment is suppressed by 

 the exclusion of air. The authors believe this parasite to be the 

 cause of the disease " pityriasis capitis," which it always accompanies 

 in large quantities. 



Influence of Light on the Growth of Yeast.* — Dr. Key finds 

 that the development of yeast proceeds equally well whether ex- 

 posed to light or in darkness. A nutritive solution was prepared, 

 containing in a litre 100 gr. of sugar, 2* 6 gr. of asparagine, with 

 20 c.cm. of a solution of mineral salts ; equal portions were placed 

 under two bell-glasses, one black and the other clear, and exposed to 

 a strong gaslight, the heat from which was absorbed by a layer of 

 water, so that the temperature was the same in both ; the number of 

 cells at the beginning and end of the experiment was counted. Of 

 eight experiments, three gave an excess in the dark glass, five in the 

 illuminated. 



Resting-form of Comma-bacilli.l — Dr. F. Hiippe has observed 

 the development of comma-bacilli without the use of staining-reagents. 

 He finds that the helix-form loses its mobility when the nutrient 

 material is exhausted, and, at high temperatures, developes to a spiral 

 form with two or more coils. The form of the helix shows but little 

 constancy, and is greatly aflfected by the rapidity of its formation, the 

 chemical nature of the food-material, or by mechanical influences; 

 very difierent forms may be found in the same culture. Sometimes 

 they resemble curved threads, or a helix drawn out flat (vibrio-form) ; 

 sometimes they are more rigid, sometimes more flexible ; and closely 

 coiled spirals are found which are sometimes flexible (spirochsete), 

 sometimes rigid (spirillum). On the same thread there may occur 

 two or even three different forms. Even the spirulina-form is oc- 

 casionally met with. When the filaments with longer coils break up, 

 the fragments are moderately uniform in habit, the commonest being 

 the more or less flexible spirochaete-spiral. No segmentation of the 

 threads is usually seen. 



At any spot in a filament, and at distances corresponding to the 

 length of a comma-bacillus, arise two globules distinctly diff'erentiated 

 from the rest of the filament, only slightly exceeding the filament in 

 diameter, but more refringent. Their membrane appears to become 

 more strongly gelatinous; they separate to a greater distance from 

 one another, but without altogether losing their connection. A second 

 comma is then formed, and there are now four globules either all at 

 nearly the same distance apart, or the two older ones at a slightly 

 greater distance than the younger ones. Six globules were sometimes 

 observed. At the spots where the segmentation began were seen a 

 large number of globules, from which projected short comma-frag- 

 ments. In one case, a previously motile comma divided directly into 

 two globules, which at first touched one another, and afterwards 

 separated to a short distance. 



These globular cells are formed between 22° and 27° C. They 



* Journ. Chem. Soc. Lond., 1. (1886) p. 387, from Bied. Centr., xv. pp. 71-2. 

 t Fortschr. der Medecin, iii. (1885). See Bot. Centralbl., xxv. (1886) p. 45. 



