402 ('. CLTFFOED DOBELL. 



AVahrlich (1890, 1891) studying a number of different 

 forms (B. subtilis, B. meg-atherium, etc.), arrived at con- 

 clusions essentially the same as those of Biitschli. He 

 believed, from their chemical and staining reactions, that 

 Bacteria contain chromatin. Young cells are homogeneous, 

 chromatic ; older cells show a reticulum of linin in which 

 granules of chromatin are suspended. The chromatin granules 

 fuse to form spores. He concludes that Bacteria are there- 

 fore really nuclei. All his work appears to be based upon a 

 study of dried cover-slip preparations. 



Zettnow (1891), using Loflfler's flagellar stain — which has 

 little value from a cytological point of view — agreed with 

 Biitschli's conclusions regarding small Bacteria. Later 

 (Zettnow, 1897) he extended his observations to large 

 Spirilla, using chiefly intra- vitam staining with methylene 

 blue, and drawing the same conclusions as before. Still later 

 (Zettnow, 1899), he examined a number of Bacteria stained 

 by Ronianowski's method, but after flame-tixation. His 

 conclusions regarding structure were essentially the same 

 once more — that Bacteria consist entirely, or in some cases 

 chiefly, of nuclear substance. 



Protopopoii (1891) found granules which stain with fuchsin 

 in a Bacillus from a cow^s tongue, and ia Actinomyces. 

 He interpreted them as being of a nuclear nature, though on 

 very slender evidence. The method of fixation is not stated. 



Wager (1891) desciibed a nucleus, containing two deeply 

 staining rods and surrounded by a very thin membrane, in a 

 Bacillus from the scum on water containing decaying Spiro- 

 gyra. The division of the nucleus is briefly described. The 

 method of fixation is not given, but it is stated that cover-glass 

 preparations wei-e stained with fuchsin. Wager (1895) again 

 described structures which he believed to be nuclei in various 

 other Bacteria, but gave only a ver}' fragmentary account both 

 of the structures themselves and of the technique employed. 



Frenzel (1891, 1892) gives a description of several species 

 of Bacteria — chiefly from a study of living cells — and draws 

 analogy between spores and nuclei. 



