124 THE LESSON OF EVOLUTION 



(Pisum sativum). He found that in crossing two 

 varieties which differed in some one character, that 

 character was generally reproduced pure, as it 

 existed in one or other of the parents. Those- 

 characters which are most persistent he called 

 dominant, while those which are seldom repro- 

 duced he called recessive. He concludes that the 

 reproductive cells of mongrels are pure, whether 

 they be dominant or recessive, " and that on the 

 average there are equal numbers of each kind for 

 each sex." 30 The so-called law of Mendel applies 

 only to self -fertilised mongrels. It is that of tha 

 offspring of self-fertilised mongrels about one half 

 will be intermediate, one quarter will be dominants, 

 and one quarter recessives. 



There is in New Zealand a very interesting' 

 example of amphimixis. In the south island there 

 are two species of Fan-tail Fly-catcher the Black 

 (Rhipidura fuliginosa) and the Pied (R. flabellifera). 

 These two commonly breed together, but no one< 

 has ever seen a bird with intermediate plumage. 

 T have been told by Mr. Edgar Stead, who is an 

 excellent and enthusiastic observer, that in union 

 nests the young are sometimes all pied, or some- 

 iimes one or more black and the others pied. So 

 that the pied seem to be the dominant species. 



Fission, Mr. Headley's suggestion that fission 

 is the principal cause of variation seems at first 

 sight very plausible ; but a little consideration shews 

 that he goes much too far. Similar irregularities 



30 See Pro. Royal Soc., Report I., to Evolution Committee, 

 ty W. Bateson and Miss Saunders, 1902. 



