404 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Central Body in the Cell of Diatoms.* — Herr 0. Biitschli has detected 
a large and conspicuous body, visible even in the living cell, in a large 
species of Surirella, in the form of a round dark granule lying in the 
hollow of the usually kidney-shaped nucleus. It appears to be the 
centre of radiating differentiations of the protoplasm, and is stained 
with moderate intensity by Delafield’s haematoxylin. 
B. Scliizomycetes. 
Structure of the Bacterial Cell.f — To determine the structure of 
the bacterial cell, Herr W. Wahrlich used twenty-four hour old cultures 
of Bac. subtilis, tumescens, carotarum, and others. These were examined 
in water, the preparations being stained and unstained. Dried cover- 
glass preparations were treated with sodium chloride, ferrocyanide of 
potash, and acetic acid, pepsin and trypsin, and 10 per cent, soda 
solution. In this way the author found that the plasma of the vegetative 
bacterial cell consists at least of two substances : one of these may be 
said to form the basis. It possesses a honeycombed structure, and from 
its micro-chemical reactions is linin ; while the other substance, which 
is found as deeply staining granules within the former substance, corre- 
sponds to chromatin. Cytoplastin appeared to be absent. 
The process of spore-formation was also examined, and it was found 
that the small granules which make their appearance within the bacterial 
cell shortly before spore-formation are nothing else than chromatin. 
From this is formed the chief part of the cell-contents, while the linin 
is devoted to the exospore, and imparts to the spores their power of 
resistance to acids and alkalies. 
The conclusion of the article is devoted to a comparison of the 
bacterial cell at different periods of its existence with the cell-nucleus 
of more highly organized cells at their various stages of development, 
and a noteworthy analogy is established between the two, the author’s 
view being that the cells of the bacteria examined by him are really 
cell-nuclei. 
Effect of Light on Bacteria.^ — Dr. T. Geisler, who has made ex- 
periments as to the effect of light on bacteria, chose for the purpose the 
typhoid bacillus, and cultivated it in 10 per cent, gelatin. From these 
experiments he concludes that a qualitative difference between the effect 
of the sun and electric light cannot be perceived, but a quantitative 
difference exists, the sunlight having a greater inhibitory effect on the 
development of B. typhosus on gelatin than the electric light. The 
light, chemical, and heat rays of both electric and sunlight act harmfully 
towards bacterial growth ; and, with the exception of the red rays, all the 
rays of the electric and solar spectra inhibit the growth of the typhoid 
bacillus, and this inhibitory effect is all the more powerful, according 
as the refractive index increases, and the wave-length of the correspond- 
ing rays becomes smaller. 
* Verhandl. Nat.-hist.-Med. Yer. Heidelberg, iv. See Bot. Centralbl., xlix. 
(1892) p. 82. 
t S.A. aus Scripta Botanica, 1890-1, 30 pp. (3 pis.). See Centralbl. f. Bakteriol. 
u. Parasitenk., xi. (1892) pp. 49-00. 
X Centralbl. f. Bakteriol. u. Parasitenk., xi. (1892) pp. 161-73. 
