herp:dity 



1S3 



of the stiuly of the results of heredit}' whicli to-day is beirifi: most 

 investigated, tlie determination of the "laws" of inheritance 

 of characteristics. 



The similarity or dissimilarity of the two mating parents is a 

 matter of much importance in regard to the results of inherit- 

 ance. To produce a fertile mating the two parents have at 

 least to be nearlv allied. We are accustomed to take this for 



Fig. 115. — Romulus, the striped colt of a horse mother and zebra father. 



(After Ewart.) 



granted, but the actual degree of phyletic relationshi}) necessary 

 in fertile mating is a point of much biologic interest. In most 

 cases both parents must belong to the same species or kiml. l)ut 

 among animals and plants there have been noted cxcei)tinns 

 to this rule, these exceptions constituting the facts of hybrith- 

 zation. 



Hybridism is practically limited to mating of difTerent 

 species of the same genera. Only in a few recorded cases liave 

 organisms of different genera mated in nature with the produc- 

 tion of oiTspring; In zoological gardens and nienagcriQ:? tho 



