156 INHERITANCE, FERTILITY, AND SEX IN PIGEONS. 



CROSSES INVOLVING THE SURATE TURTLE-DOVE, AND BLOND, WHITE, AND 

 RED RING-DOVES. 



Several of the hybrids whose nature and origin have been discussed in the 

 preceding- pages were crossed with other hybrids containing another (dark) species 

 (Spilopelia mratensis) of a genus not distantly related. This material may be more 

 appropi'iately treated here than elsewhere, though the data for the first crosses of 

 suratensis are too meager to permit any conclusion as to an association of sex and 

 color in the offspring. There is, however, evidence here to indicate that "white" 

 and "light color" tend to predominate in the season of lowest fertility (weakest 

 germs), and that the late autumn is the period of such lowest fertility. Similarly, 

 there is here further evidence that the very first egg, or clutch, of the season — 

 particularly when this proceeds from quite early in the season — is weaker than the 

 eggs or clutches that succeed it, and that the second eggs of most of the clutches 

 produced by females of pure species have less developmental energy than have the 

 first eggs of the corresponding clutches. 



Before proceeding to an examination of the data bearing upon these points 

 it is here appropriate and of interest to note the sex-ratio in these crosses of closely 

 related species. To give a more definite picture of this situation table 156 has been 

 prepared. Only those crosses in which the female w-as pure, not hybrid, are thus 

 summarized. It will be seen that the proportion of males and females is nearly or 

 quite normal to intra-specific matings, there being 64 males to 59 females. The 

 fact that some of these species are among those most extensively used in the very 

 wide crosses, from which only males arose, makes the sex-ratio noted here of con- 

 siderable significance. In many of those very wide crosses the blond ring-dove, 

 for example, was used only as female in the pair. It is demonstrated in table 156 

 that when matings were made of these more closely related species the sex-ratio 

 remained nearly or quite the same, whether the blond ring was used as male or 

 female parent in the cross. 



Four species are represented in the final offspring of this group of matings, and 

 3 species were combined in several different proportions in some offspring. This 

 permitted a study of the fractionation or divisibility of certain of the characters of 

 these species. Full reference to these points is made in Chapter XVII. Illus- 

 trations in color of some of these birds may be placed here, however, since they 

 help to make clear some features of the breeding record. The very distinct char- 

 acteristics of the Suratc turtle-dove are displayed in pi. 24. 



Crosses of the Surate turtle (see pi. 24) \\ith the blond ring (table 150) and with 

 an F2 risoria x alba hybrid (table 151) show a very high degree of infertility which 



Table 150. 

 cf Sp. suratensis (1); from dealer 9/30/07; alive 5/30/15. 



