CHAPTER XII. 



SEX-LIMITED HEREDITY IN CROSSES INVOLVING BLOND AND WHITE 

 RING-DOVES AND RELATED SPECIES. 



As early as 1896 it was found that crosses of blond and white ring-doves involve 

 a sex-limited inheritance of white color and an approach to a similar limitation 

 upon the inheritance of blond color. Soon afterward the reciprocal hybrids from 

 this cross were bred, and male hybrids were back-crossed with both pure white and 

 pure blond. Still later, crosses between whites, or blonds, or their hybrids, with 

 two other species (St. douraca and St. humilis) of the same genus were found to 

 show a similar association of sex and color. The results of these three series of 

 crosses, together with matings of some of these forms with a fifth species (Spil. 

 suratensis), are presented here. 



A full tabulation of the data will be given in the usual manner, since it is desira- 

 ble to furnish an adequate picture of the generally high degree 1 of fertility existing 

 between these closely related species. There are, too, features of the relation of 

 season to fertility and to color, and data upon "overwork" and the order of eggs in 

 the clutch, which can be presented in no other way. 1 The discussion of the data 

 for some of the crosses has been supplied by the editor. The first group of crosses of 

 blond and white ring-doves are described by the author. This description was 

 used in the presentation of the subject to a small group of zoologists in 1897. 



CROSSES OF BLOND AND WHITE RING-DOVES. 



The bird which is the subject of these remarks 2 belongs to the family Peristeridie and to 

 the genus Turtur. Turtur risoria is the name usually applied to it. The genus and species 

 are described by Salvadori (Birds of the British Museum, vol. 21, 1893, p. 415), and in a 

 footnote to the key to the species I find this remark: "It is uncertain to which species the 

 tame dove belongs." 



There is a brown variety it is technically called an isabelline color and also a white 

 variety or species. One dealer speaks of this latter species as the "white Vienna dove," but 

 on what authority I do not know. I find that authorities disagree on the question whether 

 the white ring-dove belongs to the same species as the isabelline or blond ring. 3 



1 It is not intended to schematize these results according to the current Meiulcli:in practice, for the following 

 reasons: (1) The brooding was not all carried out along Mendelian lines. (2) Whitman early convinced himself before 

 the rediscovery of Mendel's law that even in these cases the apparent segregation of "white" and "dark" is in 

 reality quite incomplete; the derived whites bear some pigment and are, in a measure, intermediates; the derived 

 blonds are quite plainly intermediate in the albax risoria cross (though some ap/taraitli/ u/v not so in the reciprocal 

 cross). (3) Again, the conclusion drawn by Dr. Whitman from the great extent and variety of his breeding work 

 is that "dominance" and " recessiveness " are matters of degree, and that by appropriate means these may be reversed; 

 this reversal being seen in such characters as fertility, color, and sex. Of course, we already have the Mendelian 

 ratios as facts, and there is no doubt concerning their existence and common exhibition. But the present work is 

 concerned chiefly with "facts about the facts," and bears upon the interpretation of the basis of heredity. The farts 

 of Mendelism have encouraged an assumption of the existence of i/iiiilitnlirr differences as the basis of contrasting 

 characters; some "facts about the facts" led the author to conclude that such differences are really nutintitatire in 

 nature, and that not gaps, but bridges, lie between contrasting characters. EDITOK. 



2 Part of a stenographic report of a lecture delivered before the Zoological Club of the University of Chicago, 

 October 13, 1897. (The copy had been somewhat revised and corrected by the author; references to the birds which 

 were demonstrated during the lecture have been adapted for this work by the editor.) 



3 Later Professor Whitman recognized these as distinct species, and treated them as StreptOpeKo, which he con- 

 sidered (partly after Salvadori) as of generic rank. See Chapter XV. EDITOR. 



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