THE INTIMATE STRUCTURE OF THE CELL 191 



later draw away, and effect complete separation. The trans- 

 verse walls that are seen in such organisms as Beggiatoa alba 

 and Thiothrix are not plasma-derived. They are transverse 

 bands of slime that have formed between the dividing cells, 

 and owe their origin to the transformation of the outermost 

 layers of the cell into slime. 



Slime Formation. — This is well developed in many of the 

 sulphur bacteria, although when the organisms arc actively 

 motile its amount is very small. The slime, when formed, 

 covers the whole organism with a closely folded mantle, which 

 subsequently hardens. In Thiothrix the slime hardens early 

 and forms a permanent sheath enfolding the inner cells, which 

 continue to grow, and to be successively thrust out of the 

 sheath. In Beggiatoa alba excessive sheath formation seems 

 to occur only under unfavourable conditions. The production 

 of slime by a mass of clustered cocci leads to the zoogloea 

 condition, and when the cocci multiply inside the slime an 

 appearance is presented of a totally different organism from 

 that from which the cocci were derived. This has led, in the 

 author's opinion, to the erroneous formation of new species, 

 and even of new genera. 



Slime formation in some cases has become fixed to the 

 extent that the cells of an organism pass their whole existence 

 inside a slime covering. This is the condition of such bacteria 

 as Thioploca, Thiopedia, and Thiodictyon. It may be presumed 

 that a continuance of this colonial habit would in time lead to 

 the differentiation of the cells, and the evolution of a multi- 

 cellular organism. Such an advance, however, has not been 

 accomplished by any of the sulphur bacteria. 



The Question of the Nucleus. — There is no readily demon- 

 strable nucleus in any member of the sulphur bacteria. Two 

 claims have been made, both of which need confirmation. It 

 will not be possible to prove or disprove Virieux's claim until 

 the behaviour of the small bodies, alleged to be the nucleus, 

 is observed during cell division. Hinze's claim that a nucleus 

 is present in Monas Miilleri rests on a somewhat sounder 

 foundation, and if it can be confirmed that the body that he 

 regards as the nucleolus breaks up into fragments during cell 



