THE CROSSING, &C, OE PIGEONS AND FOWLS. 261 



when crossed, or even fertile in excess, whilst closely- 

 allied species are almost invariably in some degree 



sterile." 



Each variety, of the Fowl, and of the Pigeon, is 

 not only defective in the mere ratio of the develop- 

 ment of its characters, but it also lacks many charac- 

 ters. Such disproportion entails the evils of close-inter- 

 breeding. Each variety possesses a feature which, if 

 joined with that of another variety, will insure a step 

 towards the original type. This conjunction of the 

 characters of two varieties, in one individual, is effected 

 by crossing; and, as a consequence, there is a bene- 

 ficial effect. 



Each variety moves along a separate, divergent line, 

 towards the true mould of the species. This advance, 

 however, produces more evil, than if all the characters 

 were suffered to lie proportionately reduced; because 

 the true ratio of the development of the characters, is 

 greatly prejudiced by this exclusive development of one 

 character. Only by the union of all the divergent lines 

 of growth, may physiological perfection be attained; 

 and, when two such divergent lines are united, in one 

 individual, the evil is measurably lessened. 



As he has asserted, that it is difficult to get highly- 

 bred animals to procreate, so he says again, that (p. 

 271, Vol. ii, Animals and Plants, &c): "Highly-bred 

 animals are liable to degeneration." As has been more 

 than once asserted, a multiplicity of divergent varie- 

 ties, in any species, implies the absence, in each, of 

 what constitutes the peculiarities of the other varieties. 



It is the disturbance of the balance of the characters, 

 23 



