66o 
Notes. 
present. Biitschli has pointed out the existence of a central body in 
various bacterial cells, the structure of which is similar in many 
respects to that of the nucleus in some forms of Infusoria ; but whether 
Biitschli’s central body is to be regarded as a nucleus or not, depends 
upon the interpretation to be placed upon certain structures which, 
according to Biitschli, are to be regarded as cytoplasmic. The dis- 
cussion of this question must, however, be reserved for the complete 
paper ; I propose now merely to give an outline of my own observa- 
tions without referring to the numerous other observers who have 
made a study of the subject. 
The first form to be described is a short Bacillus , oval in outline, 
sometimes almost of a Coccus-form, which was found forming a pellicle 
upon water containing a quantity of putrefying tadpoles. In this form 
the cell-wall appears to possess a thick gelatinous membrane which 
stains, if at all, only slightly. In the protoplast two parts can be 
distinguished — a central rod which stains deeply in fuchsin and other 
aniline dyes, and fairly deeply in Delafield’s haematoxylin, and is not 
digested by pepsin; and a slightly stainable substance in connexion 
with it, which is only distinctly visible at the two ends of the cell. 
Such a structure is perhaps the simplest to be found in any bacterial cell. 
Division of the cell is always preceded by division of the central rod. 
In other Bacteria the structure of the cell is not quite so simple, but, 
as I hope to show in the complete paper, the structure of all bacterial 
cells may be referred to this type, and they may be regarded merely as 
more or less differentiated forms of this simple one. In Spirillum 
undula, for example, numerous deeply stained bands are to be seen in 
specimens carefully stained with various aniline dyes, especially fuchsin, 
crossing the cell in a transverse direction; these vary in number and 
size in different individuals. On examining them closely we find that 
they are peripheral and in close contact with the cell-wall, and do not 
extend all across the cell. They are connected with one another by 
a layer of less deeply stained substance. They apparently increase in 
number by a more or less regular process of division, and at certain 
stages they may divide more irregularly and even form granules 
arranged at the periphery of the cell and connected together by 
a network of the less deeply stained substance. Between the simple 
form first described and this much more complicated structure of 
Spirillum undula , forms will be described which show that we are 
dealing in both cases with practically the same organization. 
