BLENDING INHERITANCE 183 



address at Cambridge University in 1908, stated that 

 what was once beheved to be the rule has now be- 

 come the exception. He goes on to say: *'One clear 

 exception I may mention. Castle finds that in a cross 

 between 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 Ears 



As a typical example of blending inheritance in 

 rabbit ears may be cited the following case : — 



A female Belgian hareAvith 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 aver- 

 age 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 at- 

 tained ear-lengths of 170, 166, 168, 160, 172, and 

 168 mm. These results are represented diagram- 

 matically in Figure 52. 



This illustration is typical of many other breed- 

 ing experiments made by the same investigators ^ 



* Castle, in collaboration with Walter, Mullenix and Cobb. "Studies 

 of Inheritance in Rabbits." Carnegie Institution Publications, Wash- 

 ington, No. 114, 1909. 



