APPENDIX 339 



four times iii the fertilisation, since sixteen individuals are included 

 in the series. Therefore the participators in the fertilisation are 



Pollen cells AB + AB + AB + AB ^- Ah + Ah -^ Ah + Ah 



+ aJ? + aB + aB + aB + ah^ah + ah + ah. 



Egg ceUs AB + AB + AB -\- AB -{- Ah + Ah + Ah -\- Ah 



+ aB ->r aB + aB + aB + ah + ah + ah -{- ah. 



In the process of fertilisation each pollen form unites on an average 

 equally often with each egg cell form, so that each of the four pollen 

 cells AB unites once with one of the forms of egg cell AB, Ah, aB, 

 ah. In precisely the same way the rest of the pollen cells of the 

 forms Ah, aB, ah unite with all the other egg cells. We obtain 

 therefore 



AB AB AB AB Ah Ah Ah Ah 

 AB Ah aB ah AB Ah aB ah 



aB , aB , aB , aB , ah , ah , ah , ah 



an j^ an _tOrf an ao ao ao ao 

 ABAb'^'^ABAb'^ab' 



or 



AB + ABh + AaB + AaBh + ABh -i- Ah + AaBh + Aah + AaB 

 + AaBh + a/? + aBh + AaBh + Aah + aBh + ah = AB 

 + Ah -{- aB + ah -\- 2ABh + 2aBh + 2AaB + 2Aah + 4AaBh} 



In precisely similar fashion is the developmental series of hybrids 

 exhibited when three kinds of 'differentiating characters are con- 

 joined in them. The hybrids form eight various kinds of egg 

 and pollen cells — ABC, ABc, AhC, Ahc, aBC, aBc, ahC, ahc — and 

 each pollen form unites itself again on the average once with each 

 form of egg cell. 



The law of combination of different characters, which governs 

 the development of the hybrids, finds therefore its foundation and 

 explanation in the principle enunciated, that the hybrids produce 

 egg cells and pollen cells which in equal numbers represent all con- 

 stant forms which result from the combinations of the characters 

 brought together in fertilisation. 



1 [In the original the sign of equaUty ( = ) is here represented by +, evidently a 

 misprint.] 



