VARIED RESULTS OF C ROSSI XG 385 



hybridising normally yields this mosaic-like result, it usually 

 turns out that the mosaic pattern was really in one or both 

 of the parents, though it may have remained quite latent. 



Exclusive Inheritance. — When two more or less different 

 forms are crossed it often happens that the offspring resemble 

 one parent exclusively. The characters of the other parent 

 remain latent. This resembles the first stage in Mendelian 

 inheritance, where the dominant characters alone find expression. 

 In old-fashioned phraseology one parent is thoroughly prepotent. 

 But if the hybrids breed true when paired inter se, or if they 

 produce forms like only one of the grandparents, or if they 

 produce a reversion to an ancestral type, or if they produce 

 something quite novel, then we are not dealing with Mendelian 

 phenomena. 



Hybridisation in General. — It is not desirable to attempt to 

 draw any definite line between the various kinds of crossings — 

 which may all be arranged on an inclined plane — for they differ 

 simply in the degree of difference between the two parents. We 

 may conveniently use the word "hybridisation" (cross-breeding, 

 outbreeding, exogamy) whenever there is a marked difference 

 between the two parents. The cases may be arranged on an 

 inclined plane. 



^.^^ . . . . Different genera. 

 _^^^^ . . . Different species. 

 ^^^ . . . . Different subspecies. 

 Different breeds. 

 . . Mutants. 

 Variants. 

 Apparently identical forms. 

 .^^^ . . . . Self-fertilisation (autogamy). 

 Parthenogenesis. 



Examples. — Individuals belonging to different genera — e.g. 

 domestic fowl and pheasant, sea-urchins, different genera of 

 orchids. 



Individuals belonging to different species — e.g. capercaillie 



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