136 THE CYTOLOGY AND LIFE-HISTORY OF BACTERIA 



is most advantageously seen upon the surface of an agar plate, there is no 

 reason to believe that it does not occur in nature. Proteus may accordingly 

 be regarded as having achieved a minor degree of cellular specialisation. It 

 is also a temporary specialisation, because the swarm filaments, which are 

 distributive in function, are the descendants as well as the parents of the 

 " somatic " cells which accumulate the energy for the swarm. In multi- 

 cellular animals and plants, although not always in fungi, the continuity o( 

 the germ plasm is very close, and the somatic cells proper have no reproductive 

 function, when once the body of the organism is elaborated. Even in the 

 case of myxobacteria, the microcysts may survive to germinate, but the cells 

 which form the stalk and envelope of the fruiting body have no 

 descendants. 



D; CHLAMYDOBACTERIAL AGGREGATES 

 (5.7) 



As far as is known, the condition in chlamydobactcria, as typified by the 

 filamentous, iron bacteria, resembles that in Proteus. The aggregates of 

 gelatinous sheaths, the by-product of metabolism, arc devoid of structural 

 specialisation, except in so far as some are dead casts left behind by the cells 

 which were responsible for their formation, whereas others are inhabited, 

 and still increasing in size. The hold-fasts by which the ends of some types 

 of filament are attached to the substrate are a possible exception to this rule. 

 Those bacteria in which the character is most strongly developed are often 

 classed as caulobacteria for precisely this reason. 



After a period of vegetative growth, motile swarm cells are produced 

 which swim away to form new colonics of filaments. There is no evidence 

 that all the cells comprising the sessile filaments may not be equally capable 

 of transformation into swarmcrs ; and indeed, what little is known of their 

 cytology suggests a close resemblance to eubacteria, in this and other 

 respects. 



