PRELIMINARY REPORT OF CROSSING TWO HEMIP- 

 TEROUS SPECIES, WITH REFERENCE TO THE 

 INHERITANCE OF A SECOND EXCLU- 

 SIVELY MALE CHARACTER. 



KATHARINE FOOT AND E. C. STROBELL. 

 OXFORD. 



Attention of cytologists has been centered during the past few 

 years on the chromosome theory that claims to offer an explana- 

 tion of sex-determination a theory due to the discovery of 

 certain morphological differences in the chromosomes of the 

 males and females of many species. This discovery is responsible 

 for the chromosome hypothesis of sex-determination an hy- 

 pothesis that awaits the test of experiment. 



Recently (Foot and Strobell, '13) we published the results of 

 some cross-breeding experiments undertaken with the aim of 

 testing the above mentioned hypothesis that the factors deter- 

 mining sex are carried and distributed by definite chromosomes. 

 The character selected to test this hypothesis was an exclusively 

 male character in Euschistus variolarius a distinct dark spot 

 which is present on the genital segment of the male only, and we 

 claimed that the method of the transmission of this spot should 

 be an index of the method of transmission of the entire male 

 genital segment. This exclusively male character the genital 

 spot is a distinguishing feature of Euschistus variolarius, but is 

 absent in E. servus. We therefore selected these two species 

 as well adapted to test the function of the so-called sex-chromo- 

 somes in the transmission of this exclusively male character. 

 Our claim that the method of transmission of the genital spot 

 may be interpreted as an index of the transmission of the male 

 reproductive organs themselves has not been accepted by two 

 critics (Morgan and Doncaster) who have recently referred to 

 our results. In reply to the criticism of these two advocates of 

 the chromosome theory of sex-determination, we quote the fol- 

 lowing from a paper now in press (Foot and Strobell, 'i4&). 



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