Generic Characters in the Coccaceae 



i8i 



really a group of eight small ones. The sarcinai in general showed 

 quite small individual units, o. i or 0.2 /* as a rule, with no constant 

 deviations. The packets are therefore entirely omitted from the 

 consideration of dimensions. 



The average sizes of the 345 cultures, not occurring in packets, 

 are grouped in convenient classes in Table 16 and plotted in Fig. i. 



TABLE 16. 

 Dimensions of 345 Cocci. 



Size, average, w . . . . 

 Number of cultures 



1 .0 



2 



The sizes of the cocci studied are evidently distributed on a fairly 

 normal curve of frequency. The mode is at 0.3^ and the curve 

 is markedly skew, with infinite extension toward the larger sizes. 

 The important practical point is that the forms measured appear 

 to behave like a fairly homogeneous series var)'ing about a single 

 mode. 



We have made tentative calculations of correlation between cell 

 dimensions and other characters, with almost entirely negative result. 

 The only property showing any relation is that of gelatin liquefaction. 



TABLE 17. 



CORREI.ATION BETWEEN CeI.L DIMENSIONS AND CeLATIN LIQUEFACTION. 



An appreciable inverse correlation is shown between the size 

 of the cell and the rate of gelatin liquefaction, the smaller cocci 

 liquefying most readily. 



3. Gram Stain. 



We have pointed out above that the reaction of the cocci to the 

 anilin-oil-iodin stain is a variable character, many forms showing a 

 positive reaction on one occasion and a negative reaction when next 

 tested. Nevertheless the test, variable as it is, shows quite constant 

 relations to other characteristics; and we feel convinced that among 

 the cocci where all characters are more or less fluctuating any prop- 



