Abstract
1) Between P and Psa, non-disjundtion occurs occasionally. In such cases, the union of two genes is so firm that they remain united permanently.
2) A probable explanation of such hundred per cent non-disjunction is attachment of two second chromosomes. The validity of this explanation has been tested from genetical and cytological observations.
3) It was assumed that in the attached strains crossing over occurs in the female with a frequency of 0.2-0.3%.
4) A number of polyploid individuals were obtained during the course of this experiment.
