Genetics of Platypoecilus III.  Inheritance of sex and crossing over of the sex chromosomes in the platyfish MYRON GORDON February 5, 1937 GENETIC evidence of crossing over between the sex G chromosomes of heterogametic individuals (XU males and WZ females) is so rare in animals as to give special significance to additional data on this occurrence.  AIDA (1921) has shown in the Japanese ricefield killifish, Aplocheilus, that the X and Y chromosomes of the male occasionally cross over. In 1930 he presented additional data on this, together with some interesting data involving aberrant sex ratios, which he interpreted as due to nondisjunction.

 In 1936 AIDA re-interpreted the abnormal sex ratios as due to sex reversal, following the suggestions of WITSCHI and WINGE.

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