BIOMETRIC IDEAS AND METHODS 67 



in regard to the logical foundation of the procedure 

 by which it is deduced, since the illustrations 

 mentioned concern themselves with qualitative 

 variations, whereas it is with quantitative varia- 

 tions that the biometrical study of inheritance 

 has had to do. As a matter of fact the case for 

 the law is made no better if this contention be 

 granted, though it is difficult to see what reason 

 exists for supposing that so-called qualitative 

 variations are not inherited in fundamentally the 

 same way as are so-called quantitative variations. 

 Every character and every variation has both a 

 qualitative and a quantitative aspect. But if we 

 consider only the quantitative aspect of the matter, 

 as has been done in much of the biometric work 

 on inheritance, the same principle of the unre- 

 liability of somatic conditions as a criterion of 

 hereditary behavior comes clearly forth from the 

 work of Johannsen 1 on beans, that of Jennings 2 

 on Paramecium, investigations regarding the in- 

 heritance of fecundity in the domestic fowl, 3 and 

 many other recent studies along similar lines by 

 various investigators. 



All of the experimental investigations referred 

 to agree in showing in a most definite and indubi- 

 table manner that there exist two distinct cate- 



1 hoc. cit. 



2 Jennings, H. S. Proc. Amer. Phil. Soc, Vol. XLVII, pp. 393-546, 

 1908. 



3 Pearl, R. Jour. Exp. Zool., Vol. 13, pp. 153-268, 1912. 



