«>8 



BACTERIA 8q 



three theories one by one, endeavoring to determine which one, in our 

 opinion, seems most probable. 



One of these theories claims that bacteria are cells of very primitive 

 organization lacking nucleus and' consisting simply of cytoplasm with 

 vacuoles. The cytoplasm contains many stainable granulations, but 

 these represent products of nutrition. Such amjpinion scarcely accords 

 with our knowledge of the constitution of the other Protista, in all of 

 which the existence of a typical nucleus, or at least of chromatic 

 elements replacing the nucleus, has been established. This view has 

 not, therefore, had many supporters. 



Another theory maintains that bac- /f^fe^x^ ^ 

 teria have a typical nucleus and are in >i««^feaiiJr tv 

 no way structurally different from ordi- CH^'' ^^ 



nary cells. This opinion was suggested 

 by Arthur Meyer, who claims to have 

 succeeded in differentiating, in a great 

 many bacteria, granules which fix nu- 

 clear stains, and of which one or often 

 several appear in a cell. These granules 

 he would consider nuclei. It seems to 

 be established, however, that the ma- 

 jority of the elements noted by Meyer ^lo.'^ez.-Bactermm gammari 

 are not nuclei, but reserve products and a filamentous bacterium from 

 common among the Pro&to and known ?|ySS°^ ^'■^''''"'^- ^'^^'"' 

 as metachromatic corpuscles. 



Vejdowsky's efforts have resulted in much weightier proofs in favor 

 of the existence of a true nucleus. In the Bacterium gammari, a 

 species discovered by him in the sections of a httle fresh water crus- 

 tacean, Gammarus zschokkei, Vejdowsky has been able to demonstrate 

 in each cell a tj^ical nucleus which is always present. This nucleus 

 appears very clearly; it consists of a colorless nucleoplasm surrounded 

 by a membrane and by one or two karyosomes (Fig. 68). The author 

 had the good fortune to ascertain in several cases karyokinetic represen- 

 tations of the division of this nucleus (a, b, c). In short, the presence 

 of this nucleus is indisputable. 



The same author discovered a similar structure in a filamentous 

 bacterium found in the digestive tract of an Annelida {Bryodrilus 

 ehkrsi) (Fig. 68, d). 



