RELATIONS OF THE COCCACE^ 35 



marks a distinct step forward. He separates such forms 

 as the gonococcus and M. catarrhalis from the other 

 micrococci by their feeble growth on ordinary culture 

 media; and distinguishes the "doubtfully chromogenic 

 forms" which produce a light yellow growth from the 

 "distinctly chromogenic" or yellowish orange forms. 



In 1905, the authors made a careful comparison of the 

 published description of 445 supposedly distinct species 

 of cocci as given by Cohn, Migula, Fliigge, Chester, 

 Sternberg, Lehmann and Neumann, Engler and Prantl, 

 Rabenhorst, Frankland, LeGros, and Woodhead. Ex- 

 amination of the literature alone, in the light of a general 

 knowledge of the characteristics of the Coccaceae, was 

 sufficient to show that most of the 445 specific names had 

 no adequate basis for existence. Slight variations in 

 morphology (the size of cells, the length of chains, 

 etc.), slight peculiarities in the appearance of colonies on 

 gelatin, slight differences in vigor of growth at certain 

 temperatures and on certain media, taken by themselves, 

 are clearly inadequate for the establishment of bacterial 

 species. If such observations are made definite by quan- 

 titative measurements and tied together by studies of 

 correlation, they may prove most helpful; but exact data 

 analyzed in this way have hitherto been wholly lacking. 

 Almost the only clean-cut facts noted in the published 

 descriptions of species among the cocci, collected by 

 Migula and Chester in their standard works, are the rela- 

 tion of the organisms to gelatin, their action upon sugars, 



