CH. IX] SUPPOSED TRANSMUTATIONS 117 



alcaligenes. The latter organism in one experiment, after 

 three passages through the guineapig, gave rise to B. coli 

 which however reverted subsequently to B. faecalis alcali- 

 genes. 



(g) From the second (laboratory) strain of B. typhosus 

 referred to above (&), after exposure to the same conditions, 

 he obtained in two different experiments B. faecalis alcali- 

 genes. The latter organism in two later experiments (in the 

 first after 5 months' further growth and in the second after 

 8 passages through the guinea»pig) gave rise to streptococcus 

 faecalis; while in a third experiment (after 18 successive 

 passages through the guinea-pig) it gave rise to B. coli which, 

 after the 19th passage, reverted to B. faecalis alcaligeiies and 

 this, after further "passages," in two different experiments 

 yielded the streptococcus faecalis. 



(h) From the same (laboratory) strain of 5. typhosus, after 

 growth in the diluted and filtered urine a different carrier 

 " I," he obtained again B. faecalis alcaligenes. 



To summarise these results even more concisely, it appears 

 that Major Horrocks was forced to the conclusion that not 

 only had an organism arisen from a strain of B. typhosus in- 

 termediate in character between B. typhosus and B. coli, but 

 that other strains of B. typhosus, derived from three distinct 

 sources, had in no less than five of his experiments undergone 

 mutation into B. faecalis alcaligenes as a result of changes 

 in their environment ; and, further, that the B. faecalis alcali- 

 genes so obtained had later, in two instances, become changed 

 into B. coli (reversion taking place in both cases, however, 

 subsequently) and, in four instances, become changed into 

 streptococcus faecalis, once after prolonged cultivation and 

 three times as the result of passage ; and, finally, that one 

 of the original strains of B. typhosus had undergone a similar 

 change into streptococcus faecalis after passage. 



Major Horrocks's statements are so startling and, if sub- 

 stantiated, would prove so revolutionary in character that they 

 demand careful examination. 



It may not be possible to disprove either his facts or his 

 inferences, but it is not necessary to do so. The onus of proof 



