44 



THE CYTOLOGY AND LIFE-HISTORY OF 



ACTERI A 



of Spirilla, each of which is about half the diameter of a typical, iinfibrillar 

 flagellum, arise in bundles from single granules, so that each bundle constitutes 

 a compound flagellum. This is considered to represent a primitive condition, 

 intermediate between that in typical bacteria and in the flagellate protista 

 (Chapter IX). 



Fig. 15 

 BACTERIAL BLEPHAROPLASTS 



A. Electron microfi;raph of Spirillum sp. showing two flagella attached to a blepharoplast. 



B. V ihrio cholerae with monfibrillar flagellum and its blepharoplast. [Sec also figs. 13, 16,57). 



The microcysts and spores of bacteria are devoid of flagella. These 

 commence to grow at germination ; usually at the pole remote from the 

 growing-point of the cell. 



Because of their muscular activity, and because they are complete antigens, 

 flagella are almost certainly composed of protein in all cases. In Proteus they 

 have been shown to consist of a fibrous protein resembling myosin. By 

 comparison with the contractile muscle protein actomyosin, however, it lacks 

 the sulphydryl groups which play an important part in this complex. 



The possession of flagella is the most important single factor suggesting 

 relationship between bacteria and the flagellate protista, rather than with the 

 blue-green algae, as is often suggested, and much of the argument concerning 

 evolutionary relationships between bacteria is based upon the evidence of 

 these structures. 



