v FORMS OF HEREDITY 247 



condition of science it is nearly impossible to foresee 



what will be the results of a crossing But we 



may assert that this method will yield very interesting 

 results, and all the more so that the crossed varieties 

 will be more dissimilar." 



This is quite true, and we cannot wonder at it when 

 we consider how many different forms heredity is 

 able to assume. Accepting Cornevin's recent classi- 

 fication, we recognise the following modes : 



1. Predominant or Unilateral Heredity ', where the 

 hereditary tendencies of one of the two mates appear 

 predominantly or exclusively in the progeny. 



2. Bilateral Heredity. Here the progeny has 

 characters of both progenitors ; and it seldom, if ever, 

 happens that the progeny has both sorts of characters 

 to the same degree, or in the same proportion ; one of 

 the progenitors has more influence than the other. 

 Both sorts of characters may fuse and combine 

 together; white and black begetting gray for instance ; 

 or may coexist, remaining separate, the progeny 

 having some traits of the father, and others of the 

 mother. In this sort of heredity four cases are possible : 

 Heredity is Direct or Crossed, Equal or Unequal. 

 These terms require no explanation. 



3. Atavistic Heredity, or Retrogression, which may 

 also be direct, crossed, or collateral. In this case the 

 predominant characters in the progeny are charac- 



