HYBRIDISM 247 



to the perfect character of either parent would be more 

 likely to occur with mongrels, which are descended from 

 varieties often suddenly produced and semi-monstrous 

 in character, than with hybrids, which are descended 

 from species slowly and naturally produced. On the 

 whole I entirely agree with Dr Prosper Lucas, who, 

 after arranging an enormous body of facts with respect 

 to animals, comes to the conclusion, that the laws of 

 resemblance of the child to its parents are the same, 

 whether the two parents differ much or little from 

 each other, namely in the union of individuals of the 

 same variety, or of different varieties, or of distinct 

 species. 



Laying aside the question of fertility and sterility, in 

 all other respects there seems to be a general and close 

 similarity in the offspring of crossed species, and of 

 crossed varieties. If we look at species as having been 

 specially created, and at varieties as having been 

 produced by secondary laws, this similarity would be an 

 astonishing fact. But it harmonises perfectly with the 

 view that there is no essential distinction between species 

 and varieties. 



Summary of Chapter. — First crosses between forms 

 sufficiently distinct to be ranked as species, and their 

 hybrids, are very generally, but not universally, sterile. 

 The sterility is of all degrees, and is often so slight that 

 the two most careful experimentalists who have ever 

 lived, have come to diametrically opposite conclusions 

 in ranking forms by this test. The sterility is innately 

 variable in individuals of the same species, and is 

 eminently susceptible of favourable and unfavourable 

 conditions. The degree of sterility does not strictly 

 follow systematic affinity, but is governed by several 

 curious and complex laws. It is generally different, 

 and sometimes widely different, in reciprocal crosses 

 between the same two species. It is not always equal 

 in degree in a first cross and in the hybrid produced 

 from this cross. 



In the same manner as in grafting trees, the capacity 



