SPIRAL TWIST A\D OPT. ACTIVITY 



91 



e 



10 



Fig. 9. Average decrease in fresh weight in starving adult dextral 

 (D) and sinistral (S) forms of the snails FrvAicicola lantzi. Abscissae: 

 Time in days; Ordinates: Weight in % of the initial value. (From 

 Gause and Smaragdova, 1939.) 



6. On the Relation hetiveen MorpJiological Inversion 

 and Molecular Inversion. Having considered the physio- 

 logical differences of the dextral and sinistral forms, we 

 shall now turn to the problem of the possible relation 

 between morphological and molecular inversions. Let us 

 at first note that the heat injury in the dextral strains of 

 Bacillus mycoides reminds one of the heat injury observed 

 when different lower organisms, such as yeast, were cul- 

 tured on unnatural isomers of amino acids (Gause and 

 Smaragdova, 1938). When the yeast Torula utilis was 

 grown on the natural isomer of leucine, which enters into 

 the composition of all living organisms, the velocity of 

 growth was that always observed in typical growth-tem- 

 perature curves, but when it was cultured on the unnat- 

 ural isomer of leucine, the increase in the velocity of 

 growth became always less and less with the rise of tem- 

 perature. 



