6 CONSIDERATIONS INFLUENCING CLASSIFICATION 



simple beginnings along this line, their knowledge of bacteria as they are known 

 today was very limited indeed. Even in 1838, when Ehrenberg published his 

 description of the types of organisms found in infusions, microscopes had not 

 yet been developed to a place where even large bacteria could be studied with 

 any satisfaction. 



By 1872, Ferdinand Cohn (Untersuchungen iiber Bacterien. I. Beitr. z. Biol, 

 d. Pflanzen., 1, Heft 2, 1872, 187-222), the botanist, began to understand that 

 a great variety of types of bacteria were in existence, and he was able to arrange 

 an outline classification on which later classifications of bacteria have been built. 

 However, his first outline classification of bacteria was scarcely pubUshed before 

 he felt that he should have expressed the relationships of the bacteria to the 

 simplest types of algae in a more intimate way. He therefore, in 1875 (Unter- 

 suchungen iiber Bacterien., II. ibid., 1, Heft 3, 1875, 141-207), drew up a second 

 classification in which he integrated the known groups of bacteria with known 

 groups of blue-green algae in a class, the Schizophyta. This arrangement assumed 

 that the bacteria had a much more intimate relationship to the blue-green algae 

 than the true fungi have to the green, red and brown algae. 



It should be noted that early classifications of bacteria were based primarily 

 upon structural characters, particularly the shape of the cells. This was a 

 natural development, as morphological characters had been found to be useful 

 in drawing up natural classifications of higher plants and animals. It is also 

 (luite natural that workers who drew up these classifications should have regarded 

 the spherical organisms that they found as being primitive in nature. Little 

 was known at that time of the distribution of bacteria in nature. It was not 

 until later that it came to be realized that the bacteria that are spherical in 

 shape are normally found on the skin or in secretions of skin glands (milk and 

 other dairy products, etc.) of vertebrates. Few cocci exist as free-living forms in 

 water or soil. Likewise, when physiological studies were made, it was found that 

 the cocci require comparatively complex foods for their existence. Few modern 

 classifications retain the arrangement in which cocci are placed first as suggested 

 by Cohn in 1872. 



Others have developed the early classifications* drawn up by Cohn, with many 

 individuals contributing to the development of a better and better understanding 

 of the evolutionary development of the bacteria. In the 1890's, two groups 

 of individuals undertook the publication of manuals describing the known species 

 of bacteria. These two groups exercised a great influence on the development of 

 systematic bacteriology. 



Migula (Arb. Bact. Inst., Karlsruhe, 1, 1894, 235-238; in Engler and Prantl, 

 Naturlichen Pflanzenfamilien, Schizophyta, 1 Teil, la, 1895, 1-44) and his 

 students began their work at Karlsruhe, Germany, in the early part of the 

 1890's, publishing various papers and books, the last of which was Migula's 



* For a more detailed discussion of outline classifications developed by bacteriologists, 

 3ee Manual, 3rd ed., 1930, 1-23; and Manual, 6th ed., 1948, 5-38. 



