THE GENUS ALBOCOCCUS 207 



flagella. It was isolated from rabbits which had died 

 of septicaemia, and may perhaps be identified with the 

 motile form isolated by Pitfield (1897) from the blood of 

 dogs and named by him Streptococcus sanguinis-canis. 

 Pitfield's organism was described as forming long chains 

 in certain media, but its white growth makes it improbable 

 that it belongs to the genus Streptococcus as we have de- 

 fined it. Two other motile cocci have been described 

 which apparently belong to this genus, M. tetragenus 

 mobilis ventriculi, Mendoza, and Planococcus casei, 

 Migula. The former resembles Alb. tetragenus in its 

 tendency to occur in tetrads, and in the possession of a 

 capsule. The latter was said to form colonies with 

 toothed edges like Catterina's form. 



It is possible that a type center of motile albococci 

 should be recognized. If so, the type form is apparently 

 related to Alb. candidus in other respects. It seems cer- 

 tain, however, that the property of motility is a rare one 

 among the cocci; and it is probable that it is highly in- 

 constant even in those cultures in which it occurs. It has 

 seemed wisest in the light of present knowledge to give 

 specific names only to those types which are apparently 

 so common as to deserve the rank of centers of variation. 

 There seems no reason to depart from this general prin- 

 ciple in the present case. Motile cocci of three distinct 

 types have been reported, types which belong in the genera 

 Albococcus, Micrococcus, and Rhodococcus, respectively. 

 Instead of labeling these forms, neither of which has been 



