36 



BIOLOGY AND TECHNIQUE 



Alg^. 



SCHYZOMYCETBS 



(Bacteria). 



Coccacea. 

 Bacteriarea;. 

 Spirillacese. 



I 



Cbyptogamia. 



I 



Thallophyta. 



I 



Lichens. 



Blastomycetes 

 (Yeasts). 



Chlamydobactefia. 



(Higher batteria.) 



Streptothrix. 



Cladothrix. 



Leptothrix. 



Actinomyces. 



Fungi. 



Hyphomycetes 

 (Moulds — Oidia). 



The special classification of the bacteria has offered still greater 

 difficulties, for the lower we proceed in the phylogenetic scale of living 

 beings, the less specialized the morphological and biological charac- 

 teristics of any group become, and the more difficult it is to establish a 

 classificai^ion which can in any way be regarded as final. It is, there- 

 fore, quite impossible to classify the bacterial varieties or species on any 

 basis which can hope to satisfy all the demands of scientific accuracy 

 and it is necessary to resort to the expedient of utilizing some one 

 characteristic which remains constant for the individual genus and to 

 base upon this an attempt at grouping. When bacteria were first dis- 

 covered, and for many years following, numerous observers contended 

 that the form of the microorganism observed was not a constant one 

 for each genus, but that cocci could be converted into bacilli or spirilla 

 according to environmental conditions. It was Cohn ^ who, in 1872, 

 first recognized the constancy of the morphology of bacteria and es- 

 tablished, upon morphological basis, a classification which, with minor 

 changes, has been retained until the present day. Such classifications 

 can not, however, be regarded as anything more thto a convenient 

 make-shift pending the day when the finer structure and true biological 

 relations of the various bacteria shall have been more accurately inves- 

 tigated. The scheme most commonly accepted at present is the one 

 given below, proposed by Migula '' : ' 



1 Cohn, "Beitrage zur Biol. d. Pflanzen," Heft 1 u. 2, 1872. 

 > Migula, "System d, Bakt.," Jena, 1897. 



