CHAPTER IV. 



JAPANESE TURTLE-DOVES CROSSED WITH A DISTANTLY RELATED AND WITH 

 A CLOSELY RELATED SPECIES.' 



The present cha]:)ter and the three following ones ileal with the breeding and 

 crossing of the Japanese or Oriental turtle-dove. The data included bear upon 

 several different subjects, but chiefly with "degree of fertility" in association with 

 longevity and sex. The relation between "weak germs" and season, crowded 

 reproduction, inbreeding, and "mutations" are touched upon at many points. All 

 of these topics are met with in the present chapter, where the first purpose is to 

 record the data for the fertility, sex-ratio, and longevity of the offsjjring of the 

 three species concerned \\hen individuals are mated (1) to their own kind, (2) to a 

 related species, and (3) to an unrelated species. 



Different individuals of the species Turtur orientalis, under even normal or 

 usual conditions, bestow very different possibilities of length of life upon their 

 offspring. When mated with their own s])ecies the strongest pairs of Japanese 

 turtles should produce offspring with a life-term of perhaps 3 to 15 years or more. 

 Data on this point will be found toward the conclusion of the chapter. When 

 crosses are made, the "width of the cross" very measurably affects (in the widest 

 crosses) the number of eggs that will hatch, and also the length of life and the sex 

 of the resulting offspring. By "width of cross" is meant the degree of phylogenetic 

 separation of the species used.= When a species closely related to T. orientalis is 

 used as the other member of the cross, more of the eggs will hatch, the young will 

 live longer, and the sex-ratio in the offspring will be more nearly that normal to a 

 mating of two T. orientalis than when a species distantly related to orientalis forms 

 the other member of the cross. The species most closely related to T. orientalis 

 is the European turtle-dove {Turtur turtur), and the most widely separated species 

 with which the Japanese turtle has been mated is the domestic pigeon. Columha 

 admista, C. affinis dom., C. tabellaria, and C. gyrans were the common i^igcons most 

 used. The external characteristics of the Japanese turtle-dove are well shown in 

 pi. 1. The common ]:)igeons are too well known to require special illustration or 

 doscrii^tion here; one is shown with its hybrid mate in pi. 3, and several are figured 

 in Volume I. There is no connected body of data to be presented on the length 

 of life of the common pigeon, but it is generally known that they easily attain 

 5 to 15 years. 



COMMON PIGEON X JAPANESE TURTLE-DOVE. 



Five female Japanese turtles were tested \\ith 7 male common j^igeons. They 

 formed 8 different matings which will be individually described; but the tables 

 which accompany these ]3agcs are relied upon to supply many points of information 

 and to permit a closer view of the essential facts. 



From the first mating {admista x orientalis, 1) 16 eggs were tested (table 1). 

 Four eggs showed no development; 3 produced embryos unable to complete develop- 



' The textual statement of this chapter has been written by the editor; all of the tabulated breeding records used 

 here are those of the author. 



= The affinities and phylogeny of the pigeons are treated in Volume I of these works. A partial sketch of the classi- 

 fication has been given at the close of Chapter II of this volume. 



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