THE ODD CHROMOSOME IN THE SPERMATOGENESIS 

 OF THE DOMESTIC CHICKEN^ 



ALICE M. BORING AND RAYMOND PEARL 



SIX PLATES 



The spermatogenesis of several birds has been described by 

 Guyer; the pigeon ('00), the domestic guinea ('09 a), and the 

 domestic chicken ('09 b) . The chickens used were of the Black 

 Langshan breed. Guyer reports for this form an X-chromosome, 

 which goes into one half of the secondary spermatocytes, thus 

 giving rise to two kinds of spermatozoa, half with X and half 

 without. If this X-chromosome is assumed to be a sex chromo- 

 some, as in so many forms, the male bird, according to Guyer's 

 account, must be heterozygous in regard to sex. 



The chicken is one of the few animals on which there have 

 been both breeding experiments and cytological work bearing 

 upon this point. Breeding experiments with the domestic fowl 

 liave furnished a great mass of the clearest kind of evidence re- 

 garding the inheritance of sex. On account of the importance 

 of the point at issue, and in order that the cumulative weight 

 of the body of independent experimental evidence may be more 

 readily appreciated, it will be well to review briefly the literature 

 regarding sex-linked inheritance in poultry and in other birds. 

 We may begin this review with the case of the inheritance of 

 the barred color pattern of the Barred Plymouth Rock which 

 has been thoroughly studied by a number of workers. Follow- 

 ing the papers of Spillman ('09 a and b) suggesting, on the basis 

 of observations of crosses of Black Langshans and Barred Ply- 

 mouth Rocks, that the female fowl was heterozygous, and the 



^ Papers from the Biological Laboratory of the Maine Agricultural Experiment 

 Station, No. 46. 



53 



