An Introduction to a Biology 



(if this word may be used of two objects) the germ-cells 

 together * like counters in a hat ; and that, in the resultant 

 hybrid, the germ-cells differ from the two which took part 

 in its formation, only in actual number ; for the propor- 

 tions are the same (50% dominant and 50% recessive) and 

 the discontinuous condition of the germ-cells is the same, 

 inasmuch as a germ-cell represents either a dominant or a 

 re*cessive, and never partly one and partly the other ; in 

 fact, it is no more possible to produce such an intermediate 

 stage than it is possible to get a pink counter by shaking 

 up scarlet and white ones in a hat. To look for a moment 

 at the offspring of the hybrids : Mendel says that the " ex- 

 tracted " dominants (the dominant offspring of the hybrids) 

 will always breed true ; and that the same is true of the 

 " extracted " recessives : this can be illustrated in our 

 imitation hybridisation experiment by placing half the RR'a 

 in one hat and half in another ; it is evident that nothing 

 but reds can be got from " matings " from these two hats. 



It is also a fundamental part of the Mendelian principle 

 (in fact, it seems to me to be its foundation-stone) that 

 the " extracted " hybrids will produce the same kind, and 

 proportions of the three kinds, of offspring as the first 

 hybrid ; for if half the .RTF's are put into one hat and half 

 into another it is evident that random matings will give 

 25% RR, 50% RW, and 25% WW as before, and, what is 

 more, that they will continue to do so (so long as we keep 

 up the number of counters) for however long we continue 

 the process, that is to say, for howsoever many generations 

 it is carried on. 



(6) A POINT OF DIFFERENCE BETWEEN GALTON'S AND 

 MENDEL'S THEORY 



I do not propose to discuss here the difference between 

 the Mendelian principles and the statistical conception of 



1 Of course the germ-cells fuse : it is the character-bearing elements 

 which are thus mingled. 



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