lO Darbishire, Mendelian Principles of Heredity. 



validity of the two theories, inasmuch as it is a matter 

 about which the Mendehan and Galtonian predictions 

 are totally at variance ; and because I think the time has 

 not yet come for such statements, as, for example, this 

 from the pen of Professor Castle (:03(3:, p. 228): "It" 

 (Mendel's theory) " thus meets the two-fold requirement 

 of a scientific theory, a statement of phenomena and an 

 explanation of them; the "law of ancestral heredity" 

 attempts only the first of these two things, and even here 

 fails lamentably. It will be thus seen that the claims of 

 Mendel's law are much greater than those of Galton's law." 

 The italics are mine {see Karl Pearson, Grammar of 

 Science, p. 121 ; and also in this connection Pearson :04). 



(7) New Conceptions based on Mendel's Investiga- 

 tions. 



I will only refer to three of these : the curious reader 

 is referred to Bateson's " Mendel's Principles of Heredity," 

 p. 26. 



{a) The first of them is " the purity of the gametes in 

 regard to certain characters" (Bateson :02, p. 26). This 

 generalization is based on the often repeated fact, that (to 

 take an example) in respect of the colour of the seed a 

 germ-cell of a pea, whether it be contained by the pure 

 yellow or pure green race, or by the hybrid or any of its 

 descendants, is absolutely pure. And it is believed that it 

 will continue to be pure in respect of these characters 

 until a specific upheaval takes place, when a new character 

 will arise by the process of discontinuous variation. 



(f) The second is the conception of unit-characters 

 (I.e. p. 27-28) in respect of which the gamete is pure. Such 

 units seem to correspond to that in the adult organism 

 which Weismann sought in the germ. These unit- 

 characters, as we have seen, usually exist in pairs in such 

 a way that one is dominant and the other recessive ; and 



