MORPHOLOGY AND CLASSIFICATION 143 



right angles so as to produce plates, and it also includes those 

 which divide in an irregular fashion so that no definite geometric 

 figure results. Sarcina includes those cocci which divide in three 

 planes at right angles to each other, in turn, so as to produce 

 cubical masses of cells. Planococcus is similar to Micrococcus 

 in all respects except that its members are motile and possess 

 flagella, and Planosarcina includes the motile forms which are 

 in other respects the same as the forms included under Sarcina. 



COCCACE^E Cells spherical, without endospores. 

 Streptococcus Division in one plane, forming chains of cells; 



non-motile; without flagella. 

 Micrococcus Division in two planes, forming flat plates of 



cells, or irregular, forming masses of cells irregularly 



grouped; non-motile; without flagella. 



Sarcina Division in three planes, forming cubical or package- 

 shaped masses of cells; non-motile; without flagella. 

 Planococcus Division in two planes, forming flat plates 



of cells, or irregular, forming mass of cells irregularly 



grouped; motile; bear flagella. 

 Planosarcina Division in three planes, forming cubical 



or package-shaped masses of cells; motile; bear flagella. 

 These genera have not been generally adopted by bacteriolo- 

 gists. The terms Streptococcus and Sarcina are, however, 

 quite generally employed as the generic names for the organisms 

 of their respective groups as defined by Migula, as they had 

 been used in this way before. Micrococcus, however, is commonly 

 employed as a general term for all the members of the family 

 Coccaceae, and Planococcus and Planosarcina have not been used, 

 because bacterial forms belonging to these genera are exceedingly 

 uncommon and it may even be questioned whether those which 

 have been described might not better be classed with the cylin- 

 drical bacteria, in which motility is of frequent occurrence. 

 Other terms in common use as generic names for certain cocci 

 are Diplococcus and Staphylococcus. A diplococcus is a double 

 coccus, two spheres attached together. This grouping by twos 



