116 INHERITANCE, FERTILITY, AND SEX IN PIGEONS. 



This mutant (21) hatched September 28, 1906, from the second egg of the clutch. . . . 

 In the midst of a mating with a mourning-dove she was noted on July 9, 1908, to have 

 weak legs (probably she was weakening before this was observed). In her breeding she 

 began strongly to transmit her juvenal (mutant) pattern, but as she weakened the male 

 gained control and produced the normal type (italics are the author's). (K, C 000) 



The result of breeding from the first of the daughter "mutants" is given in 

 table 94. It is clear that the mutational mark was strongly inherited in this the 

 second generation. Its inheritance in the third generation is shown under jmir 2 

 of the same table.' A glance at table 95 will show that one of the normal daughters 

 of the original mutant gave no evidence of power to produce mutants when mated 

 with a complex Zenaida x Zenaidura hybrid. 



The several succeeding tables already referred to in another connection show 

 that none of the many combinations of Zenaida, Zenaidura, or of their hybrids * 

 give any suggestion of forms similar to mutant No. 21 and her mutant progeny. 



In this Zenaida mutation (No. 21), then, we have to do with a striking de- 

 parture from the normal, with a character Avhich exists in the juvenal plumage 

 only, with a character which is firmly fixed in heredity; and the bird which originally 

 displayed this character was known to have originated from a germ which was 

 developed under those conditions which have elsew^here shown themselves to be 

 associated with "weakness" of germs. 



The data on the inbreeding of three pairs of Zenaida-Zenaidura hybrids (mat- 

 ings of brother and sister) are given in table 97. The result, in all the matings, 

 is a low fertility and a shortened life-term of the offspring. 



An analysis of the sex-data obtained from all of the matings recorded in this 

 chapter is attempted in table 99. Three points are considered: (1) the sex-ratio 

 (upper row) from (a) pure-bred matings, from (6) matings of hybrid males with 

 pure-bred females, (c) various hybrid combinations (two groups) ; (2) the ratio of 

 males to females (middle row) from eggs laid before July 1 ; and (3) the relation of 

 the order of eggs in the clutch (lower row) to sex, in mating in which (a) pure 

 females and (b) hybrid females were the producers of the eggs. 



By reference to the table it will be seen that in matings of carolinensis x 

 carolinensis the ratio of males to females is 10 d' : 12 9. When crosses were made, 

 using pure (not hybrid) females (carolinensis and vinaceo-rufa) , this ratio was 20 cf : 

 14 9 . From crosses in w^hich the female is hybrid the ratio was 15 cf : 14 9 . 

 The corresponding figures prior to July 1 are, 4:6,11:7, and 8 : 4. The relation of 

 sex to egg of clutch is of interest, and the effect of hybridization upon this order 

 is well shown. Pure-bred females produced the two sexes in each of 15 clutches; 

 12 of these threw males from the first and females from the second egg, the 

 reverse in 3 cases. But hybrid females yielded 6 such pairs in which only 3 threw 

 the sexes in the more usual order, and in an equal number of pairs this order was 

 reversed. 



' This stock has been maintained by the editor since 1910, and has thrown normals and mutants much as in the 

 record given above. The breeding of the "mutant" series was actively done during 1911, 1912, and 1915. A further 

 statement concerning the later results will at some time be published. — Editor. 



' Zenaida and Zenaidura present several contrasting characters to which slight reference is made in the tables. 

 It will be noted that for most of these characters Whitman had found that the characters "fractionated," and that 

 pvcn in the Fj and complex hybrids there was often little evidence of segregation. One of these hybrids is shown 

 in pi. 20. — Editor. 



