THE MENDELIAN PHENOMENA 15 



hybrid generation, are allowed to self-fertilise. The 

 seed set by the dwarfs produces only dwarfs. This 

 is what we should expect, if we look at the tails and 

 dwarfs in the genealogical table from the point of 

 view of their stability in breeding, that is to say 

 according as to whether they produce their own kind 

 only, or both kinds, namely tall and dwarf. If we 

 look back through the pedigree of the dwarfs of the 

 second hybrid generation, we do not come to a dwarf 

 until we reach the pure dwarf parent of the cross. 

 This pure dwarf, as we know, breeds true. We 

 might, therefore, expect that the dwarfs will breed 

 true when they reappear in the second hybrid genera- 

 tion. And we see that they do. 



Before we consider the offspring of the tails in 

 the second hybrid generation, let us look back in 

 their pedigree and see if we can form any idea as to 

 what their offspring will be. In the case of the 

 dwarfs of the second hybrid generation we had to go 

 back two generations, namely, to the parents of the 

 cross, before we met with an ancestor bearing the 

 dwarf character. But in the case of the tails we have 

 only to go back one generation — to the first hybrid 

 generation — to find a tall. But this hybrid, although 

 it resembles the pure tall externally, differs from it 

 in its breeding properties. The pure tall produces 

 only tails ; from the point of view of its breeding 

 properties, it is stable. But the hybrid tall pro- 

 duces both tails and dwarfs, in the proportion 

 of three tails to one dwarf in every four ; it is 

 unstable. That is to say, if we look back through 



