BLENDING INHERITANCE 189 



It should be noted further that 50 out of 64, or 77 

 per cent, of these hybrids of the second filial genera- 

 tion would have an ear-length between 140 and 180, 

 thus approximating a "blend" closely enough to be so 

 classified upon a casual inspection. 



If it should be found, moreover, that excessive ear- 

 length in rabbits is due to more than three duplicate 

 determiners, the possibilities of getting anything but 

 an apparent blend would be much decreased. 



Furthermore, the fact that the fractional ear- 

 lengths of the hybrid rabbits in Castle's experiments 

 bred approximately true in the second and subsequent 

 filial generations, may also be explained by the Nilsson- 

 Ehle hypothesis. 



For example, half lop lengths, according to this 

 explanation, are those with three doses of the deter- 

 miner for excess ear-length. It follows that the 

 progeny of two rabbits each carrying three doses of 

 a determiner will likewise, after the reduction during 

 the maturation of the germ-cells, have three doses of 



the determiner 



It would be interesting to breed rabbits having ears 

 of one-eighth lop length in which, according to the 

 foregoing hypothesis, there presumably would be 

 present only a single determiner for excess ear-length, 

 with ordinary short-eared rabbits having no excess 

 ear-length, in order to see if the expected Mendelian 

 three-to-one proportion for a monohybrid would ap- 

 pear in the progeny. 



