186 THE MENDEL JOURNAL 



can be pure bred in the old sense, can be bred for succes- 

 sive generations from a particular race, and yet not be 

 homogeneous ; indeed, may be most markedly hetero- 

 geneous. Blue Andalusian fowls, for instance, may be 

 bred for indefinite generations from blue Andalusians 

 and yet not a single homogeneous blue Andalusian bird 

 will be obtained by the process. The Andalusian race 

 thus bred will, in fact, remain a most heterogeneous one, 

 throwing both black and splashed white individuals in 

 each generation. Such instances can be multiplied, 

 but this particular one will suffice. 



The mere fact then that the Barred Plymouth Rock 

 hens which form the material of Dr. Pearl's biometrical 

 investigation " had been carefully and closely selected 

 in their breeding for more than 25 years " is, by itself, no 

 guarantee of the homogeneity of the race, and still less 

 is it any guarantee of the homogeneity of the comb 

 characters. Neither is there any greater degree of 

 guarantee introduced by the fact that " during the last 

 nine years they have been ' line bred ' — that is, no fresh 

 blood has been imported." The statement therefore 

 that : "It would be difficult to find anywhere material 

 for the study of variation more homogeneous than that 

 dealt with here," has really no scientific meaning at 

 all. It has a fancier's meaning, but nothing more. 

 There is no proof forthcoming of the homogeneity 

 of this material in the scientific sense. On the 

 other hand, the three plates containing 96 figures 

 of very diverse single combs, which illustrate the 

 authors' paper, is an eloquent testimony to the hetero- 

 geneity of the material. We think these plates constitute 

 such clear evidence of this that there remains little doubt 

 in our minds " that it would be difficult to find any- 

 where " more heterogeneous material. 



Now what is it the Biometricians want us to under- 

 stand by the term " a homogeneous pure-bred strain of 

 hens " ? What is a homogeneous race ? We doubt 

 whether any such thing exists. Are we asked to beheve 

 that this race of Barred Plymouth Rock hens is homo- 

 geneous in all the multifarious characters of each indivi- 

 dual ? Or that it is so only in respect of those characters 



