478 The Ohio Naturalist [Vol. XV, No. 6, 



the expected Mendelian ratio when two factors were required to 

 produce the brown color. When he crossed a red and white- 

 grained wheat, the F-2 generation segregated into the ratio of 63 

 red to 1 white grain. From this Nilsson-Ehle reasoned that three 

 independent factors were required to produce the red color. 



Although the operation of Mendel's law of heredity with 

 respect to qualitative characters has been amply proven, there is 

 a considerable doubt in the minds of miany foremost geneticists as 

 to whether or not quantitati^•e characters are inherited in a 

 Mendelian fashion. It has only been within the last few years 

 that students of heredity have turned their attention to the prob- 

 lein of inheritance of quantitative characters. 



The first man who worked definitely with quantitative char- 

 acters seems to have been Lock in 1906 (36) who crossed a tall 

 race of maize with a shorter race and obtained an F-1 hybrid 

 intermediate in size between the parents. The F-2 plants showed 

 no segregation when crossed with one of the parents. Lock 

 showed that the height of a plant is not inherited in a simple 

 Mendelian fashion. 



Castle in 1909 (S) worked with the ear-lengths of rabbits and 

 discovered what he called "blending inheritance". In sumiming 

 up his own work Castle says, "A cross between rabbits differing 

 in ear-lengths produces an off-spring with ears of intermediate 

 length, var\'ing about the mean of the parental ear-lengths. 

 * * * * A study * * * * shows the blend of parental 

 characters to be permanent. No reappearance of the grand- 

 parental ear-lengths occurs in the F-2 generation, nor are the 

 individuals of the second generation as a rule more variable than 

 those of the first generation of cross-breeds. * * * * ^Yhe 

 linear dimensions of Jthe skeletal parts of an individual approx- 

 imate closely the mid-parental dimensions". 



Ghigi in 1909 (22) crossed a Paduan fowl and a bantam and 

 found that the size of body and eggs of the F-1 cross-bred individ- 

 uals were intermediate between the parent races. Only a limited 

 number of the later generations were grown and these showed no 

 segregation of size characters. 



Mendelians have not recognized the validity of any so-called 

 "blending inheritance" except that which Castle has shown. 

 And these results on the ear-lengths of rabbits ha\'e been explained 

 according to the Mendelian notation by Lang, whose explanation 

 is recognized as possible by Castle. vSomc Mendelians object to 

 this "blending inheritance" on the grounds that the number of 

 individuals grown was not large enough to prove that segregation 

 does not occur in the F-2 generation and Castle has admitted the 

 possibility of this fact. 



