THE STRUCTURE OF BACTERIA. 39 



Assuming that life originated upon our 

 planet, the first living things must have been 

 so organized that their metabolic processes 

 were more like those of plants than of animals ; 

 in a word, the primitive organisms must have 

 been holophytic, since to holophytes alone are 

 saprophytes able to attach themselves. It is 

 therefore suggestive that, besides physiological 

 correspondences to be noted later, the structure 

 of the gonidia-forming or arthrosporous bacteria 

 shows a progressive differentiation or evolution 

 from the simplest bacterial forms and species 

 through to the Cyanophycece, a group of blue- 

 green algae which may be regarded as an unde- 

 veloped branch of the plant kingdom. On the 

 other hand, the formation of endospores and the 

 possession of flagella are facts that indicate 

 phylogenetic relations with the monads or flag- 

 ellates, a group usually reckoned as animals. 

 Physiologically also a double affinity is mani- 

 fested, since bacteria display almost the same 

 capacity for building up organic substance as 

 for breaking it down. 



It was remarked by Cohn that a complete 

 parallelism existed between the genera now 

 regarded as arthrosporous bacteria and certain 

 groups of the fission-algae (Spaltalgen}. Cohn, 

 indeed, already departing from his purely 

 morphological standpoint, established two 



