An Introduction to a Biology 



inheritance, but to consider one part of the hypothesis put 

 forward by Mendel, which is at variance with Galton's 

 theory. I refer to the phenomenon of segregation. We 

 have seen what Mendel says (see Bateson, :02, p. 57). 

 But this is flatly contradicted by the Galtonian generalisa- 

 tion, according to which the greater number of generations 

 a given hybrid is from the first hybrid (i.e., of course, also 

 from the parents of the hybrids), the fewer pure reces- 

 sive and dominant forms is it likely to produce when mated 

 with another hybrid of its own generation (Darbishire, :04 ? 

 pp. 23 et seq.). 



I refer to this point (which at first sight may appear 

 insignificant, but in reality is not) because it seems to me 

 to afford a means of deciding between the relative validity 

 of the two theories, inasmuch as it is a matter about which 

 the Mendelian 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 Pro- 

 fessor Castle (:03a, 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 Pear- 

 son, " Grammar of Science," p. 121 ; and also, in this con- 

 nection, Pearson, :04). 



(7) NEW CONCEPTIONS BASED ON MENDEL'S INVESTIGATIONS 



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 

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

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



