CHAPTER IV 



HYBRIDISM 



The alleged sterility of hybrids a stumbling-block to evolutionists 

 Huxley's views Wallace on the sterility of hybrids Darwin 

 on the same Wallace's theory that the infertility of hybrids 

 has been caused by Natural Selection so as to prevent the 

 evils of intercrossing Crosses between distinct species not 

 necessarily infertile Fertile crosses between species of plants 

 Sterile plant hybrids Fertile mammalian hybrids Fertile 

 bird hybrids Fertile hybrids among amphibia Limits of 

 hybridisation Multiple hybrids Characters of hybrids 

 Hybridism does not appear to have exercised much effect on 

 the origin of new species. 





alleged sterility of the hybrids pro- 

 duced by crossing different species 

 has long proved a great stumbling- 

 block to evolutionists. Huxley, in 

 particular, felt the force of this objection to the 

 Darwinian theory. If the hybrids between 

 natural species are sterile, while those of all 

 the varieties which the breeder has produced 

 are perfectly fertile, it is obviously quite use- 

 less for evolutionists to point with pride to the 

 results obtained by the breeder, and to declare 

 that his products differ from one another to a 

 greater extent than do many well-recognised 

 species. 



in 



