1 14 Marshall Ward. — On the Characters , or 
3. Colonies hollow, the cells in a single peri- 
pheral layer ...... 
Colonies solid throughout, and filled with 
cells ....... 4 
4. Cells few, and joined in regular families, 
each with a definite number . 
Cells in larger numbers, aggregated in irre- 
gular colonies, each with an indefinite 
number ...... 
5. Cells shortly cylindrical, isolated, or two or 
more loosely joined .... 
Cells as long cylinders, united into filaments 6 
6. Filaments isolated or matted together . 7 
Filaments in rounded gelatinous matrix 
7. Filaments unbranched .... 8 
Filaments- with false-branching . 
8. Filaments rectilinear . • . . .9 
Filaments spiral or curved . . . .11 
9. Filaments short and distinctly segmented . 
Filaments long, segments usually obscure . 10 
10. Filaments very slender .... 
Filaments thicker ..... 
11. Filaments short, spiral with a few turns, or 
merely curved : stiff .... 
Filaments longer, and with numerous spiral 
turns, and flexile ..... 
Cohnia. 
Sarcina. 
Ascococcus. 
Bacterium , 
Myconostoc . 
Cladothrix. 
Bacillus . 
Leptothrix. 
Beggialoa. 
Spirillum. 
Spiro chaeta. 
[Appendix — Sphaerotilus and Crenothrix . ] 
In the meantime the controversy had begun as to the 
meaning of ‘ species ’ among the Schizomycetes. Billroth, in 
1874, had stated his conviction that all the forms are mere 
varieties of one fundamental species, and some experiments 
of Buchner’s (1882) with Bacilhis anthracis and B. sub tills 
(which Buchner thought he had proved to be convertible one 
with the other) seemed to support the idea. Naegeli, with 
whom Buchner was associated, took up a similar view, and 
thus arose the split, already referred to, between the ex- 
tremists who regarded the polymorphism of the Schizomy- 
