CH. IX] OF TRANSMUTATION 129 



first experiment (p. 238, exp. II) — known after this as "35 A " — 

 was further tested (p. 243) by successive passages through 

 the peritoneal cavity of the guineapig. The fluid removed 

 after the 8th passage when subcultured into broth showed 

 short-chained cocci and diplococci but when subcultured on 

 to agar gave, in addition to these cocci, the original bacillus 

 " 35A." The latter in broth again yielded the short-chained 

 cocci and these on agar gave a bacillus once more — but this 

 time not " 35 A " but a fermenting coliform organism. 



The original strain of B. faeealis alcaligenes (obtained 

 in Exp. II, p. 238) was a second time tested in the same way 

 (p. 243). It showed no change in character until the 18th 

 passage when it gave rise to a fermenting bacillus of the B. 

 coli type which on the 19th passage reverted to B. faeealis 

 alcaligenes. This last-named organism, after 7 more passages 

 in one experiment and 8 more passages in another, gave rise 

 to a fermenting B. coli type of organism " in pure culture " 

 and this, on planting in broth, yielded B. fa^ecalis alcaligenes 

 once more but, with it, cocci corresponding to 8. faeealis. 

 The latter after 3 passages remained unchanged. 



Criticism. The transition from the non-fermenting B. 

 faeealis alcaligenes to the fermenting coli type and back 

 again, may be regarded as no more than another example of 

 variation similar to those quoted in an earlier section of this 

 work. Again, in the " passage " experiments, one or other 

 type may have been an invader from the gut, the apparent 

 reversion at a later passage merely representing the de- 

 struction of the invader which had not been " hardened," so 

 to speak, by previous passages. Only one guineapig was used 

 for each " passage " experiment in a series of passages. If 

 more than one had been used some check would have existed 

 on possible errors due to this cause. The repeated transitions 

 from B. faeealis alcaligenes to 8. faeealis and vice versa 

 are more difficult to explain, for 8. faeealis appeared 

 not only after passage but during cultivation also on artificial 

 media. One is 'almost forced to the conclusion that Major 

 Horrocks was dealing with a mixed strain of the two organisms 

 and that changes in the conditions of growth at one time 



D. 9 



