s/'iir\L T\\ 1ST A\n. oi'T. Acrn ITY 93 



Similar data were obtained also in the study of the 

 growth of the- mould Aspergillus niger on the optical 

 isomers of leucine and valine. 



The same relation between lenii)erature and rate of 

 growth is thus observed in the unusual strain of Bacillus 

 mycoides growni on natural substrates and in the yeast 

 or fungi grown on unnatural substrates. In both cases, 

 there nuist be an inhibitive factor of growth. It may be 

 conjectured that in the case of yeast or fungi the un- 

 natural isomer of the amino acid dissolved in the cul- 

 ture medium surrounding the cells caused a retardation 

 of growth because its spatial contiguration did not coin- 

 cide with the spatial configuration of the basic constit- 

 uents of protoplasm. In the case of Bacillus mycoides 

 the retardation of growth in the unusual form would be 

 caused by the presence inside of the cells of the unnatural 

 optical isomer of some organic substance which partici- 

 pated in the determination of the morphology of the 

 cell. 



7. Morpliological Inversion and the Theory of Spiral 

 Growth. The investigations on various physiological 

 properties of dextral and of sinistral strains in Bacillus 

 mycoides and in Fruticicola lantzi have brought out the 

 two following points : ( 1) In the optical properties of their 

 protoplasm these strains are alike. This follows from 

 their behavior towards optically isomeric nutritive sub- 

 stances. It has, furthermore, been confirmed by direct 

 observations made by Kiesel, Efimochkina and Rail 

 (1939), wdio isolated the same natural amino acids from 

 both dextral and sinistral strains of the snail Fruticicola 

 lantzi. (2) The inverted individuals of both bacteria and 

 snails are physiologically weaker than the typical ones. 

 These observations suggest that while in the typical in- 

 dividuals the organic substances which participate in the 

 determination of the twist might well have the same laevo- 

 rotatory configuration as the other constituents of proto- 

 plasm, in the inverted individuals some enzymatic dis- 

 turbance might have occurred. 



