1895.] Vegetable Physiology. 849 
lus, hay bacillus, ete.) When the bacillus dies the flagella loose their 
power of swelling. The flagella often remain till the last, i. e., after 
the membrane and contents of the bacillus has disappeared. This 
ready swelling which is always at right angles to the long axis, makes 
the flagella in stained preparations always thicker than natural. The 
sprouting of the flagella from the body of the cell and their subsequent 
increase to full length consumes sufficient time so that its phases can be 
fixed and studied. In Spirillum undula it takes place before completed 
cell-division and from that end of the cell previously destitute of fla- 
gella. Continued cultivation in strong salt solutions, e. g.4 to 5 per 
cent NH,C1, prevents motility, but does not interfere with the forma- 
tion of the flagella. By movements of neighboring bacilli the flagella 
are often twisted into strands which are sometimes very large. 
, In Bacillus subtilis the spore is generally found in non-flagellate rods 
forming the pellicle, rarely in free swiming flagellate rods. The fla- 
gella of bacteria are not drawn back into the cell during spore forma- 
tion. Inyolution forms of Bacillus subtilis bear no flagella, but in the 
involution forms of some other bacteria they are not thrown off. All 
motile bacteria possess flagella, and these are the sole organs of move- 
ment. Flagella are polar or diffuse according as they are restricted to 
one end of the cell or occur on any part of it. Polar flagella vary in 
number from one to several, and this number is characteristic for dif. 
ferent species, except when the cells are dividing polar flagella are al- 
ways at one end. The flagella of the bacteria are neither threads of 
protoplasm which can be thrust out and drawn back, nor dead append- 
ages of the membrane moved by the protoplast. The substance of the 
flagellum possesses a life of its own, and the power of swelling and self- 
contractility. With the protoplast, of which they are a part, the fla- 
gella appear to be only loosely connected, yet the little protoplasmic 
remnant which in plasmolysis often remains attached to the base of the 
flagellum, and sometimes connects it with the shrunken protoplast is 
certainly to be regarded as a sign of such morphological union. In 
connection with the physiological diagnosis of the bacteria a morpho- 
logical basis for classification is to be sought, and this the author thinks 
he has found for the rod-shaped bacteria in the number and position of 
the flagella and the shape of the spore-bearing cells. The author's 
classification is probably a step in the right direction, and will certainly 
lead to renewed efforts to determine the number and position of the 
flagella on a great variety of microérganisms, but, in the present state 
of our ignorance, it cannot be considered anything more than tentative. 
It ought not to be adopted until it has been tried thoroughly to see 
