Phenomena of Inheritance 



due not to the real fusion or blending of inheritance factors but 

 -to varying combinations of numerous or multiple factors, accord- 

 ing to the Mendelian rules. The Mendelian principle of segrega- 

 tion has been found to be of such general occurrence that there 

 is a strong probability that it is universal,' and that all cases of 

 "blending" inheritance are due to incomplete dominance or to 

 multiple factors. 



Maternal Inheritance. Another case which seems at first 

 sight to be non-Mendelian is what may be called "maternal in- 

 heritance" since certain characters are invariably derived from the 

 mother and not from the father. Among these are the polarity, 

 symmetry and pattern of the egg and of the adult animal which 

 is derived from it (see p. 196). These characters are of such a 

 general sort that they may not be recognized as phenomena of 

 inheritance at all, and yet they form the background and frame- 

 work for all the other characters. They do not come equally 



FIG. 36. INHERITANCE OF SIZE IN RABBITS. The skulls of two parents 

 are shown in I and 3, of their intermediate offspring in 2. (From Castle.) 



