Marks , employed for classifying the Schizomycetes . 1 1 5 
cetes as universal, and those who committed the error of 
paying too little attention to the existence of polymorphism 
in the group. 
As usually happens in such cases, the truth lies somewhere 
between the extremes, and the reader unacquainted with the 
literature cannot do better than consult De Bary’s beautiful 
fourth lecture on this subject, where the evidence for and 
against is weighed with the fairness and thoroughness so 
characteristic of that gifted master of morphology. 
Van Tieghem, in 1884, proposed to take into account the 
planes of division of the cells as furnishing the chief bases for 
dividing the Schizomycetes into three primary groups, thus = 
TABLE III. — Van Tieghem , 1884. 
I. Divisions in one plane only. Thallus filamentous, or forming 
aggregates of segments. 
A. Simple forms. 
(a) Non-sheathed. 
(i) Of minute spheroidal cells, in gelatinous matrix or 
free. May be more or less seriate. 
Micrococcus . 
(ii) Elongated in one plane, and free. 
* Rodlets short and at once free. 
Bacterium . 
* * Rodlets longer, and may remain for a time in 
series. 
Bacillus . 
* * * Filaments. 
Leptothrix . 
(iii) Elongated in spiral form. 
* Short comma-like twisted rodlets. 
Vibrio. 
* * Longer and helicoid. 
Spirillum. 
* * * Longer still, and with numerous turns. 
Spirochaete. 
