544 The Philippine Journal of Science 1913 



ondary colonies. Only cells of apparently normal morphology 

 were selected. All of the above series of selections were made 

 within a month after the original selection. 



About five months after the first selections from strain 

 105200, a new lot of cells was selected from it. The culture 

 had been kept on ordinary agar at room temperature with 

 occasional transfers to keep it viable. It had never grown on 

 a maltose-containing medium. Of 60 isolations, 52 gave typical 

 blue cultures, 6 typical red, while 2 gave partial red with no 

 secondary colonies. To test the composition of one of the par- 

 tially red strains, 9 single cells were isolated from it, and, as 

 a control, 13 from one of the typically red cultures. The cul- 

 tures from the 9 of mixed type gave all mixed color with no 

 secondary colonies, while the 13 red gave all pure red cultures. 



Nearly ten months after the first series of selections a new 

 lot of single cells was isolated from the original stock of 

 dysentery strain 105200. The culture had been kept at room 

 temperature on ordinary agar. It had been transferred at about 

 monthly intervals to fresh agar, and had had in all about 10 

 transfers since the hanging drop in which the original single 

 cell had been isolated. In this third series 123 cells were 

 isolated, and the cultures grown from them tested on maltose 

 agar, before a maltose-fermenting type was found. This, how- 

 ever, was typical, exhibiting a clear red color throughout the 

 whole tube within twenty-four hours after sowing. No sec- 

 ondary colonies were formed. Of the 122 nonfermenting 

 strains, all formed secondary colonies; in some very few and 

 in others so many as to redden the whole tube. However, 

 there was no possibility of confusing such cultures with a 

 "red" variant, since the color appeared in the former only after 

 several days and after a very large number of secondary colonies 

 had been formed. No partially red strains were found, such 

 as occurred in the second series. 



In this third series difi:"erent lots were selected at a time, 

 the selections extending over a period of some days. In each 

 lot of selections a fresh broth culture was made from the 

 original agar culture in order to obtain freshly growing cells 

 for isolation. 



So, in all series, 205 isolations were made, and from these 

 11 (about 5 per cent) of the red variants were obtained. 



Either the two varieties exist side by side for months on 

 ordinary agar, or the maltose-fermenting variations are being 

 continually formed from the stock. The proportion of acid 

 formers is the smaller, 5 in 21 in the first series, 8 in 60 in 



