orr. A(:ti\ .. // hredity asd environment 67 



acter of optical activity in secondary constituents of pro- 

 toplasm and its independency on the external conditions 

 indicates that some physiological mutations peculiar to 

 some specific strains of bacteria must have occurred 

 some time in the past in those of them which produce opti- 

 cally unusual isomers. 



Let us now attempt to penetrate into the nature of the 

 process by which a given isomer arises instead of its 

 antipode. This problem is directly related with the study 

 of some of the basic principles which underly the forma- 

 tion of physiological mutations. 



3. Mechanisms Controlling the Production of a Given 



Optical Isomer. 



a. Production of Dissymmetric S u b- 

 stances from Symmetric P h e n y 1 - G 1 y o x a 1. 

 The observations of various authors concerning the trans- 

 formations of phenyl-giyoxal, a substance deprived of 

 dissjmimetry, into mandelic acid which possesses an asym- 

 metric carbon atom, are important in the study of the 

 question here discussed. These transformations are cat- 

 alysed by enzymes known generally as ketonaldehydemu- 

 tases. Starting from a symmetric initial product these 

 enzymes synthesize directly, without any intermediate 

 racemic stage, the optically active mandelic acid. Fur- 

 thermore, ketonaldehydemutases of ditferent species of 

 bacteria synthesize from the same initial product sub- 

 stances which are optically inverse, as the results re- 

 ported by different authors and represented in Table 13 

 show. 



The action of the ketonaldehydenmtases is probably to 

 be attributed to the asymmetric state of these enzymes. 



There are many observations more or less directly re- 

 lated to those just given. Neuberg and Simon (1926), for 

 example, found that an acetic-acid bacterium, B. ascendes, 

 produced laevorotatory amyl alcohol from a racemic 

 valeric aldehvde, while another bacterium of acetic acid 



