DM HAKY AND IirKI'I'F/S CLASSIFICATION 71 



one and the same organism, which, on account of its origin, he named Bacterium 

 lactis. 



It must not be understood that similar errors were confined to the island of 

 Britain ; on the contrary, they attained their culmination on the Continent in 

 the assumptions of HALLIEH (I.) concerning the metamorphosis of ono fungus 

 into another. It need, ther< fore, be small matter for surprise that the Austrian 

 surgeon Til. BILLROTH (I.), in a comprehensive work published in 1874, not only 

 attributed all infectious diseases to the agency of a single species of bacterium, 

 susceptible of multiform modifications, but also considered all known bacteria 

 generally as vegetation forms of this one species, viz., Coccobacteria septica. This 

 observer was supported by the botanist NAGELI (VI.), in so far that the latter 

 declared that no necessity existed for the division of the bacteria even into only 

 two specifically different forms. This opinion he still maintained in 1882, not- 

 withstanding the appearance in the interim of a work by Cohn containing a 

 number of fresh data calculated to complete and support the theory of difference 

 of species in bacteria. This treatise has already been mentioned in 24, because 

 its author upheld the relationship of the fission fungi to fission algae and advocated 

 their collection into one group, Schizophytes. As at present, however, we are not 

 concerned with the relationship of the Schizomycetes to other organisms, but with 

 the separation of the former into genera, we must confine ourselves to remarking 

 that the new classification in the said treatise rested too exclusively on morpho- 

 logical characters to be of practical value. 



69. De Bary and Hueppe's Classification. 



Gradually an accumulation of facts arose which afforded a basis whereon a 

 new system of grouping the fission fungi was attempted. Differentiation based 

 on cell form only was still considered justifiable up to 1878, but could no longer 

 be maintained in the face 

 of incontrovertible observa- 

 tions made, in the course of 

 the following years, with 



absolutely pure cultures of fc-^^^^^^ eziiSiZ)esni3 <m*z& 



various species of bacteria, 2 



and all leading to the same 



conclusion, that mutability, 



i.e. modification of form, 



unquestionably does occur 



in the fission fungi. This OOQ0^@QQC3SSM3(2) 



knowledge is the result of * 



various researches, amongst 



which may be mentioned i gcpgo^^Q^ffiP^Q ^I5i5P(ci3ti^Si!D(S3^^i^^^ggi^i^^g 



in 1879, that of E - CH - S 



HANSEN (II.) on Bacterium FlG< 30. Bacte. ium merismopedioides. 



aceti and B. Pasteurianum ; Found ln the mud of the river Panke (Ber ii U ). 



in 1882 those of W. t A tliread form breaking lip into : 2. long- rods ; 3. short rods : 

 ZOPF (HI.) On Bacterium 4. cocci ; 5. a chain formed of rods of different lengths. 



merismopedioides (Fig. 30), (After Zopf.) Ma-n. 700. 



and by H. BUCHNER (VI.) 



on Bacillus subtilis ; in 1883 that ^ KURTH (I.) on Bacterium Zopfii (Fig. 31), 



afterwards also examined by H. SCHEDTLER (I.) ; in 1885 that of G. HAUSER (I.) 



on a few species of putrefactive bacteria of the genus Proteus : and others. The 



adherents of Koch at first unconditionally opposed the theory of the pleomorphism 



of bacteria ; but, not being able to sustain this view in the face of the facts 



