MENDEL' 8 LAW. 271 



Nothing has been said so far concerning the external appearances 

 of the hybrid, whether it is intermediate between the parents, or 

 resembles one or the other of them. The efforts of investigators 

 since the time of Kolreuter have been directed to the futile attempt 

 to find some law which would enable the breeder to predict the appear- 

 ance of this hybrid. In general, this can not be done, with our 

 present knowledge. There are two cases to consider. In certain 

 instances hybrids are strictly intermediate between the parents. In 

 others they are unlike either parent. These cases will be noticed 

 later. In the more common case the hybrid either shows a parent 

 character fully developed or shows it not at all. A parent character 

 which is fully developed in the hybrid is said to be 'dominant'; if 

 it is apparently absent it is said to be 'recessive.' In my work with 

 hybrid wheats, beards have always been recessive, hence the designa- 

 tion of the hybrid as Sb. 



It will now be seen that, externally, the progeny of the hybrid 

 will consist of only two types, one type (B), constituting one fourth 

 of the progeny, being like one parent, and the other, constituting three 

 fourths of the progeny, resembling the other parent. Of this three 

 fourths, one part (S) is actually like one parent, and will produce 

 progeny like itself. The other two parts (Sb) are hybrids, and will 

 produce progeny of all the types, exactly as the original hybrid did. 

 Plants of the type 8 may easily be separated from those of the type 

 Sb by planting the seed of each plant separately, and noting the 

 character of the progeny. 



The above diagram may easily be extended to any desired number 

 of generations. Extended to the third generation it is: 



B 



S 



Sb 



B 



Sb 



S 



Assuming that each of the types S, Sb and B are equally produc- 

 tive, and mixing and sowing all the seed of each generation, the fol- 

 lowing table shows the percentage of each type in each generation 

 to the sixth: 



Generations. 

 1 

 2 

 3 

 4 

 5 

 6 



Here it is seen that the hybrid, based on a single pair of antagon- 

 istic characters, tends to split up into the two parent types. A hybrid 



