BACTERIA 105 



volutans) the cilia have connection with one of the chromatic grains of 

 the diffuse nucleus. There is a chromatic filament starting from the 

 base of the cilium and ending in connection with a chromatic grain, 

 similar to the organisms with flagella in which the flagellum is in 

 relation to a basal chromatic grain (blepharoplast). 



' The Higher Bacteria* 



The so-called higher bacteria include some of the spiral forms, at 

 least the larger spirochsetes, the thread or trichobacteria, and the 

 sulphur or thiobacteria. 



The spirochaetes and trichobacteria contain so many forms of 

 interest that their form and structure needs special consideration. 



The Larger Spirochaetes. — Spirochaetes differ so much among 

 themselves that it seems necessary to divide them into two groups. 

 The members of one of these groups, the small spirochaetes, are prac- 

 tically identical with the true bacteria, and naturally fall in the family of 

 the Spirilliacea. Members of this group, however, so gradually approach 

 the other group, the large spirochaetes, that it is difficult to draw a line 

 of separation between the two, yet the large spirochaetes resemble in 

 so many essential details the trypanosomes that they are usually placed 

 as a coSrdinate genus with them under the flagellates — a sub-class of 

 the Protozoa. The larger spirochaetes are described as follows: 



Form and Size. — ^In form the spirochaetes are long, very thin and 

 flexible spirals. Their length is usually not less than twenty times their 

 breadth. Some forms are as long as 500 /t. It seems probable that 

 some of them are flattened and hence in form are more hke a spirally 

 bent ribbon than rod. 



Motility. — ^These organisms move very rapidly under normal con- 

 ditions. The character of the movement may be of three kinds: 

 (i) Lashing, eel or snake like; (2) undulatory, compared to the flapping 

 of a sail in the wind; (3) rotation, similar to a cork-screw when pushed 

 into a cork. 



Reproduction. — Multiplication is by means of binary fission. If 

 these forms are to be considered as bacteria, the division would be 

 expected to be by means of transverse partition walls. A number of 

 workers, however, have described a process" of longitudinal division. 



• Prepared by W. D. Frost. 



