CERTAIN CROSSINGS OF JAPANESE DO\ _>'.! 



Enough is known of the history, nature, and causation of then deviatio,, 

 "mutations," some of which have been shown to "breed true," in uial.lr 

 to predict that they will arise only or almost exclusively from such weakened u. 



FERTILITY AND LONGEVITY IN PURE-BRED JAPANESE TURTLE-DOVES. 



It remains to indicate the normal percentage of fertile eggs produced by 7'. 

 orientalis when pairs of individuals of this species are muled together, :i ,,d further. 

 to supply data upon the sex and longevity of the offspring of th.-e mating f,,, 

 comparison with the very limited life-terms noted particularly in cro thi- 



species with a distantly related one. 



The presentation of the data in a complete and tabulated form will, moreover, 

 serve two other necessary objects. First, these tables assist, as do other, of \\^ 

 book, in a demonstration of the relation that exists between season of hatching 

 and of longevity of the offspring, and the further facts of //////,// difference* ,,, 

 the capacity of parents, due to age, health, overwork, etc.. to produce.-! ronu. ^ ni\-. 

 In the second place, many of the young whose origin i- given in these table.- 

 later studied extensively as parents; the all-important features of the germinal 

 foundations from which they grew can be shown adequately, owing to the asso- 

 ciations just noted, only by means of such tabulations. This holds specially true 

 of the "mutations" which appear at the extreme end of the record: and t> 

 "mutations" become the subject-matter of the succeeding chapter. 



The one breeding record available for T. turtur is presented at this point. It 

 much resembles the records for orientalis which are to follou . Table Hi showe that 

 of 9 eggs tested, 8 were hatched; there is no definite record for the other one. The 

 shortest life-term is 4 months, and one of the young was alive and breeding at 

 51 months. The two longest-lived birds were from the second clutch of the sea-<,n: 

 the egg that probably failed to hatch, and the bird of shortest life-term, were from 

 the last (fifth) clutch of the year, laid July 26-28; 3 males and 1 females are known 

 from this family. 



Especially complete records are available for the results of -I of ."> mat ings in 

 pure Japanese turtle-doves. 6 From pair 1 there were 21 tests, and. as is shown in 

 table 17, all were hatched; 2 eggs, the first pair of the second reason, were poorly 

 incubated, but both developed to hatching. Here again the young of lon_ 

 life-term arose from early (not the "very earliest '") eggs of the season: the birds 

 from the last eggs died youngest. Neither the question of age nor of possible 

 relationship of the two birds of pair 1 can be definitely answered: they were im- 

 ported together and their short-lived offspring may be inbreds. That the term of 

 life of their offspring is too short is indeed a "time fuse" set at about :{ months 

 is apparent. The death of both the parents early in 1 HOC* and the lameness of the 

 sire indicate weakness and possibly old age as contributory cause- of their weakened 

 germs. 4 males and 4 females are known from this family. 



The data for pair 2 are very incomplete (table 18). 1 .--> were obtained only 

 from an unfavorable season of the year. The parents were imported together and 

 may have been related. They were overworked. 6 of their 11 eggs were deserted, 

 for 1 there is no record; probably 3 eggs produced embryos and 1 showed no 

 development. Both parents died soon after these eggs were produced. 



6 Matings involving inbreeding of Japanese turtles are serially eoiisi.leml in tlie next rliapler. 



