Hybrids, Varieties, and Species 249 



it is clear that the phenomena must keep nearer to the 

 normal the less the deviation is from the type. 



This type is conditioned by the fact that the two or- 

 ganisms that fertilize each other belong to the same small 

 or elementary species. They have then, on the whole, 

 the same characters, even if these are, according to their 

 environment in various degrees of development. There 

 are no differences among them independent of this, at 

 least if we consider the cumulative effect of uniform in- 

 fluences in the course of several generations. 



As soon as such independent differences occur, and as 

 soon therefore as there are present constant contrasts, 

 which are retained in the sequence of generations and 

 cannot be blended by environment, we call the sexual 

 union of two individuals a crossing or a hybridization. 

 If the contrasts are slight, we call the two races varieties, 

 if they are greater, they assume the rank of species. The 

 crossing of varieties keeps quite near to normal fertiliza- 

 tion ; that of the species deviates the more the slighter the 

 relationship between them. The crossing of varieties 

 forms a type complete in itself, that of the species forms 

 a series which descends from almost normal processes, 

 by gradual progress, to a complete reciprocal sterility. 

 The variety-hybrids are fertile like their parents, but in 

 the species-hybrids the diminished fertility indicates ab- 

 normal phenomena either in fertilization or in the ex- 

 change of the units. 



We must therefore discuss these two groups sep- 

 arately, and we shall begin with the varieties. 



In daily life and in horticulture, any thing that deviates 

 from the normal is called a variety. Even the new forms 

 obtained by crossing are quite commonly counted among 

 the varities. In science, therefore, the word would really 



