OTHER PIGEON HYBRIDS AND HHKKDING OF CERTAIN SPECIES. 165 



(table 162). The data for fertility of the Senegal x blond and white ring cro 

 both in the primary cross and in the resulting hybrids, is therefore higher than will 

 be found in the family cross next to be considered. It will .soon appear thai the 

 sex-ratio from the two groups of crosses genera and family furnishes ;i parallel to 

 this difference in fertility. Where infertility is greatest, and the cause of this infer- 

 tility is width of cross, the ratio of males to females is also highest (table 107). 



Migratorius x risoria and alba-r/xor/u lii/ltritls. Two crosses of these forms, 

 which arc separated by differences of family rank, showed a high percentage of 

 infertility; several embryos incapable of hatching were formed; and a notable frac- 

 tion of the young died very soon after hatching. The 8 offspring which survived 

 were all males (table 165). 



The male species concerned in this mating is the now extinct wild American 

 passenger-pigeon. The above-described hybrids, together with the two listed 

 immediately below, are perhaps the only known hybrids of this remarkable species. 

 The male passenger-pigeon is shown in pi. 28, the female in pi. 29, and one of the 

 hybrids from the migratorius x alba-risoria x risoria-alba cross is also shown in pi. 30. 

 The intermediate nature of the hybrid becomes clear from an inspection of the 

 illustration. This topic is further discussed in Chapter XVII. 



Migratorius x alba. This record is short, though similar to the preceding. Two 

 males were produced. The very first egg of the series and the last 3 of the season 

 were wholly infertile. 



Miscellaneous crosses. The three crosses listed in table 166 require but little 

 additional discussion. The damarensis x risoria-alba cross (pair 1) is a mating of 

 related species, and the fertility seems high and the term of life moderately long. 

 The chinensis x suratensis mating (pair 2) is also one between related species of the 

 genus. The fertility record here falls below that of the preceding cross, and the 

 term of life of the offspring is shorter. The leuconota x livia cross (pair 3) tells us 

 only that offspring may be had from this cross. The last of these crosses (pair 4 of 

 table 166) supplied more adequate tests and is of greater interest. The genera 

 involved in that cross Melopelia and Streptopelia belong to different subfamilies, 

 and the table indicates again the very high degree of infertility of such crosses. 

 Only three birds were hatched from the 18 or 20 tests; there were produced, more- 



TABLK 161. 



<? Scnegal.-risoria (TS-R2). 4/lU/Ut); 2/20/11; 22 mo. 

 9 St. alba; age unknown. 

 A 1. 5/15/10 TSRA 1 disappeared 2/5/11 to 11/4/13. 



B 1. 7/24 TSRA 2 darker than B 2; disappeared 7/5/11 to 11/4/13. 



9B2. 7/26 TSRA 3 light ruddy blond; dead 5/7/13. (AA 



TABLE 162. 



c? Scncg.-risoria hyh. (22) ; 8/S/()'.i; 11 I'S.'ll; son; pale yellow . >< 

 9 St. risoria (6): :w unknown; dam; yrllow eye. 



A 1. 4/16/10 TS-HR 1 disappeared 7/5/11-11/4/13 (or, died ? 9 7/2*. 13; darker than A 2). 



A 2. 4/18/10 TS-RR2 disappeared 7/5/11-11/4/13 (or, is cf or d 1 9 alive 10/1/14; li K hU-r than A 1). 



B 1. 5/29.. ..TSRR1 disappeared 7/5/11-11/4/13 (or. dii-d ? 9 7/2S/13). 



B2. 5/31 TSRR2 disappeared 7/5/11-11/4/13 (or, is d* or <f 9 alive Hi 1 Hi. 



C 1. 6/30 TSRR3 disappeared before 7/5/11. 



?cTC2. 7/2 TS-RR4 alive 10/1/14; is n <f , or hermaphrodite. 



D 1. 9/5 TS-RR5 probably died early; darker than D 2. 



D 2. 9/7 TS-RR 6 probably died early ; lighter than D 1. (AA 7) 



