140 CONN, HARDING, KLIGLER, FROST, PRUCHA AND ATKINS 



noticed to a striking extent on any other medium. In the 

 group number, the point devoted to chromogenesis refers to the 

 color produced on beef-extract agar. 



Diastatic action on starch. Provisional method. Use beef- 

 extract agar containing 0.2 per cent of soluble starch. Pour 

 into a petri dish, and after hardening make a streak inoculation 

 on its surface. Incubate at 37° for organisms of series I and 

 III, at 25° for organisms of series II and IV. Determinations 

 for the group number shall be based upon results obtained on 

 the seventh day. To make the test, flood the surface of the 

 petri dishes with a saturated solution of iodine in 50 per cent 

 alcohol. The breadth of the clear zone outside of the area of 

 growth indicates the extent of diastatic action. If over 2 mm. 

 in width on the seventh day it shall be recorded as " strong;" 

 if under 2 mm. as "feeble;" if no clear zone is present, as 

 "absent." 



This method requires some modification, e.g., reducing the 

 amount of peptone in the medium, for organisms that grow so 

 rapidly as to cover the entire surface of the plate in seven days, 

 thus leaving no room for a clear zone outside. 



The group-number is a brief means of recording the salient 

 features of the organism. It is primarily a summary of the 

 physiological characteristics just discussed. As each of the 

 determinations is made, the proper figure for that place in the 

 group number is to be checked or underscored. After com- 

 pleting the determinations, the entire group number is to be 

 written in at the place left for it on the chart. The genus symbol 

 should precede the group number. The present group number, 

 adopted by the Society in 1907, was intended for use with the 

 generic names of Migula. As Migula's genera are not in such 

 general use today as they were ten years ago, a revision of the 

 group number on some other basis is now being undertaken by 

 the committee, and will be discussed in Part II of this report. 



Brief characterization. On the right hand margin of page one 

 of the chart is a place for recording by a + or — sign other 

 important characteristics of the organism (primarily cultural) 



