M O N E R A 



ply rapidly by continuous cleavage, remain joined to- 

 gether. This may hap])en in two ways. When the 

 social bacteria secrete large quantities of gelatine, and 

 remain distributed in this, we have the zoogloca (as in the 

 case of the aphanocapsa and glceocapsa among the chro- 

 macea). If, on the other hand, the long-bodied bacilli 

 remain fastened together in rows, we get the knotted 

 threads of Icptoihrix and heggiatoa (which may be com- 

 pared with the oscillaria). And, if these threads go into 

 branches, we have cladothrix. Other coenobia of bac- 

 teria have the appearance of disks, the cytodes dividing 

 in a plane, usually in groups of four (as in mcrismopcdia), 

 or of cube-shaped packets when they are in all three 

 directions of space (sarcina). 



The two classes of bacteria and chromacea seem, in 

 the present condition of our knowledge, on account of 

 their simple organization, to be the simplest of all living 

 things, real monera, or organisms without organs. 

 Hence we have to put them at the lowest stage of the 

 protist kingdom, and must regard the difference between 

 them and the most highly differentiated unicellular 

 beings (such as the radiolaria, ciliated infusoria, dia- 

 tomes, or siphonea) as no smaller than the difference 

 (in the realm of the histona) between a lower polyp 

 (hydra) and a vertebrate, or between a simple alga (ulva) 

 and a palm. But if the kingdom of the pirotists is badly 

 divided, on the older rule, into a plant kingdom and an 

 animal kingdom, the only discriminating mark we have 

 left is the difference in metabolism ; in that case we have 

 to include the plasmophagous bacteria in the animal 

 kingdom (as Ehrenberg did in 1838) and the plasmo- 

 domous chromacea in the plant kingdom. The remark- 

 able class of the fiagellata, which includes ciliated uni- 

 cellulars of both groups, contains several forms which 

 are only distinguished from the typical bacterium by 

 the possession of a nucleus. If it is true that in some of 



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