SPINA L TW Tf< T AND OPT. AdlVITY 8 1 



other hand, one can see here the proof of the fact that 

 the basic features of the whole plan of structure of an 

 organism can be the result of the action of a single gene. 



''What kind of influence this gene exercises on the 

 structure of the ovum, we certainly do not know. As a 

 hypothesis I can express the suggestion that this or 

 other type of cleavage is here determined by the presence 

 in the protoplasm of the ovum of the right or of the left 

 optical isomer of some organic substance. This sub- 

 stance goes out of the nucleus of the ovum during the 

 ripening of the latter, forming itself preliminarily in 

 connection with corresponding genes of the chromosome 

 apparate of the ovocyte. Hence it may be inferred that 

 both genes of a given couple of allelomorphs are optical 

 isomers in respect to each other. ' ' 



Koltzotf 's hypothesis is, of course, not the only possible 

 interpretation of the observed facts. The optical inver- 

 sion of genes is certainly possible, but a change of their 

 chemical properties, without the inversion of their con- 

 figuration, may also be supposed. In the latter case the 

 optical inversion of some organic substance determining 

 the structure of the animal would take place only in a 

 subsidiary reaction. The facts discussed in the preceding- 

 chapter would confer about the same degree of proba- 

 bility on the hypothesis of gene inversion and on the 

 hypothesis of a chemical modification of the genes with- 

 out inversion. 



The solution of some basic biological problems de- 

 pends on the answer to this question. According to the 

 first interpretation, the substance of the genes which 

 determine the morphological structure of an animal would 

 belong to the group of secondary protoplasmic constit- 

 uents, those which play the role of storage substances or 

 of products of metabolism. These products would then be 

 quite important in the mechanism of evolution. 



2. Morphological Dissymmetry luuJ Morphological In- 

 version in Bacillus Mycoides. The typical strain of Bacil- 



