BLENDING INHERITANCE 177 



address at Cambridge University in 1908, stated that 

 what was once believed to be the rule has now become 

 the exception. He goes on to say: "One clear excep- 

 tion I may mention. Castle finds that in a cross be- 

 tween the long-eared lop rabbit and a short-eared 

 breed, ears of intermediate length are produced; and 

 that these intermediates breed approximately true." 



Let us examine this "one clear exception" a little 

 more closely. 



7. THE CASE OF RABBIT EAES 



As a typical example of blending inheritance in 

 rabbit ears the following case may be cited : 



A female Belgian hare with an ear-length of 118 mm. 

 was crossed with a male lop-eared rabbit with an ear- 

 length of 210 mm. The average of these ear-lengths 

 is 164 mm. Five offspring from this pair had ear- 

 lengths, when adult, approximating this average as 

 follows: 170, 170, 166, 156, 170, of which two were 

 females and three were males. When from this litter 

 one of the females measuring 170 mm. in ear-length 

 was subsequently crossed with her brother having an 

 ear-length of 166 mm., two litters were produced in 

 which the individuals when adult attained ear-lengths 

 of 170, 166, 168, 160, 172, and 168 mm. These 

 results are represented diagrammatically in Figure 36. 



This illustration is typical of many other breeding 

 experiments made by the same investigators 1 upon the 



1 Castle, in collaboration with Walter, Mullenix and Cobb. 

 "Studies of Inheritance in Rabbits." Carnegie Institution Publi- 

 cations, Washington, No. 114^ 1909. 



