COMPARATIVE STUDY OF THE COCCI 47 



of small sarcinae appear like large single cells. The 

 observations on the stained preparations were controlled 

 by careful examinations of the slides prepared for the 

 study of the Gram stain, as noted later. 



We distinguished two primary types of morphology, 

 depending upon the presence or absence of packets. 

 In the first group occur the streptococci, which produce 

 pairs, long chains, and irregular groups; and the 

 intermediate micrococci, which show pairs, short chains, 

 fours, and irregular groups: while the sarcinae include 

 organisms which produce fours, irregular groups, and 

 packets, as well as those extreme forms which show 

 only packets. None of these differences, except the 

 presence or absence of packets, appear on agar with 

 sufficient constancy to be determined definitely. For 

 distinction between streptococci and micrococci the 

 observation of broth cultures would perhaps be valuable; 

 but the appearance of the agar culture to the eye is 

 sufficient to distinguish the former group. 



Dimensions. The cocci exhibit a range in size from 

 o.i to 2.0^, with considerable variation between indi- 

 vidual cells in the same culture. We were somewhat 

 surprised to find that we could demonstrate no definite 

 relation between size and the age of cultures, or the 

 conditions of cultivation. In a series of preliminary 

 studies the same organism was grown on seven kinds of 

 media and examined at intervals during a period of two 

 months. The maximum size, in different cultures, was 



