56 MORPHOLOGY AND CULTURE OF MICROORGANISMS. 



CLASSIFICATION. 



The classification of bacteria was early recognized by Mueller as a 

 matter of difficulty, since he says: "The difficulties that beset the in- 

 vestigation of these microscopic animals are complex; the sure and defi- 

 nite determination (of species) requires so much time, so much of acu- 

 men of eye and judgment, so much of perseverance and patience, that 

 there is hardly anything else so difficult." Early investigators found it 

 difficult to decide whether bacteria are plants or animals, and nowadays 

 we are finding it as difficult to decide upon a system of classification. A 

 great many systems have been proposed, but many of them are untenable 

 because those who proposed them were ignorant of or unconcerned by the 

 rules adopted by systematists in other lines. The only system that seems 

 worthy of continued life is that of Migula, who is a trained botanist. This 

 system, with slight modifications, is given below. In this system, the 

 characters which separate the genera are morphological ; while physiologi- 

 cal characters, including cultural, are used for the differentiation of 

 species and smaller groups. One of the rules adopted by systematists 

 in other lines is the binomial rule. In the violation of this rule, bacteri- 

 ologists have been great sinners, and some of the names proposed by 

 Migula and others following his system are quite different from those by 

 which well-known forms have been christened by their discoverers. 



CLASSIFICATION OF MIGULA (MODIFIED). 



The bacteria are phycochrome-free schizomycetous plants which divide in one 

 two, or three planes. Reproduction takes place by vegetative multiplication (fission). 

 Resting stages in the form of endospores are produced by many species. Motility is 

 noted in some genera, and this is due to flagella. In Beggiatoa and Spirochseta the 

 organs of locomotion are not definitely known. 



I. Order: Eubacteria(true bacteria). 



The cells are devoid of any nucleus (Zentralkorper) and free from sulphur and 

 bacteriopurpurin, colorless or faintly colored. 



I. Suborder: Haplobacterinae (lower bacteria). 



I. Family: Coccaceas (ZOPF) MIG. 



The cells are globular when in a free state, but in the various stages of division 

 appear somewhat elliptical. A few species in this family are motile. Cell division 

 takes place in several directions of space. Frequently the cells remain attached to- 

 gether, and under these conditions usually show some flattening of the cell at the 

 point of junction with the cell next to it. 



Genus : Streptococcus BILLROTH. 



The cells are globular and do not possess any organs of locomotion. Cell division 



