Ill 



GOOD FROM CROSSING. 



Chap. XVII 



CHAPTEE XYII. 



ON TH 



*-F 



EFFECTS OF CROSSING, AND ON TH 



OF CLOSE INTERBREEDING. 



EVIL 



- I 

 ■ 



DEFINITION OF CLOSE INTERBREEDING 



AUGMENTATION OF MORBID TENDENCIES 



GENERAL EVIDENCE ON THE GOOD EFFECTS DERIVED FROM CROSSING, AND ON THE 

 EVIL EFFECTS FROM CLOSE INTERBREEDING — CATTLE, CLOSELY INTERBRED ' HALF- 



WILD CATTLE LONG KEPT IN THE SAME PARKS 



SHEEP — FALLOW-DEER — DOGS 



RABBITS 



PIGS 



FOWLS — PIGEONS 



BENEFITS DERIVED FROM CROSSING 



WHEAT, AND FOREST-TREES 



ORIGIN OF HIS ABHORRENCE OF INCESTUOUS MABBIAGES 



PLANTS, GENERAL CONSIDERATIONS ON THE 

 MELONS, FRUIT-TREES, PEAS, CABBAGES 



HIVE-BEES 



ON THE INCREASED SIZE OF HYBRID PLANTS, NOT 



EXCLUSIVELY DUE TO THEIR STERILITY 



ON CERTAIN PLANTS WHICH EITHER 



NORMALLY OR ABNORMALLY ARE SELF-IMPOTENT, BUT ARE FERTILE, BOTH ON THE 



CROSSED WITH DISTINCT INDIVIDUALS EITHER OF 



MALE AND FEMALE SIDE, WHEN 

 THE SAME OR ANOTHER SPECIES ■ 



CONCLUSION. 



gam m cons 



vigour, 



rom an occasional 



between individuals of the same variety, but belonging 



, lias not been 



distinct famil 



between d 



largely or 



frequently discussed, as have the evil effects of 



interbreedi 



But the former point is the mor 



is more d 



of the two, inasmuch as the evidence 

 evil results from close interbreeding • are difficult to detect, for 



ate slowly, and differ much in degree with dif- 



tney accumii 



ferent species; whilst the good eff 



follow a cross are from the first manife 



hich almost invariably 



It should, how 



be clearly understood that the advantage of close interbreedi 



9 



as 



r as the retention of character is concerned 



nd 



able, and often outweighs the evil of a slight loss of 

 tional vigour. In relation to the subject of domestic; 



hole question is of some importance, as too close interbi 



th the improvement of old 



1 



and especially 



formation of 



It 



bearing on Hybridism ; and perhap 



hen any form has become 



is important as indirectly 

 n the extinction of species, 



rare that only a few ind 



