INCREASE OF HEREDITARY POWER. 187 



type. And these hereditary powers are very largely under 

 our control, to be increased or diminished by our own course 

 of action. 



If we take two animals to breed together, both possessing 

 a strong similarity of type, the result we shall have will be 

 an offspring possessing the like character, but in a higher 

 degree. The result of putting together two animals of a 

 strong similarity of characteristics is not only to perpetuate 

 their corresponding peculiarities, but to intensify them in the 

 offspring; that is, if the parents actually possess a striking 

 similarity of t}^)e in any given point, each successive gener- 

 ation which they produce receives an increase of hereditary 

 force, or an increase of power in transmitting its peculiar 

 stamp upon its young. It is a cumulative power. But if 

 this hereditary power accumulates, and becomes stronger 

 and stronger, with a strong similarity in the parents to start 

 from, it absolutely and invariably diminishes, if the parents, 

 instead of possessing similarity of character, really possess an 

 opposite or antagonistic character. 



It reminds us of the familiar and well-known principle of 

 mathematics, that two plus or positive quantities multiplied 

 together will produce a far larger plus or positive quantity 

 as the product ; while if we multiply two unlike quantities, 

 a plus and a minus, for instance, the result will be a minus, 

 or negative quantity. 



Professor Tanner, who is entitled to be regarded as high 

 authority on this and kindred subjects, puts the matter some- 

 what like this : — 



Suppose, for example, we have a well-bred ram, that, by 

 long and careful breeding through several generations, has 

 acquired certain strong and valuable hereditary powers ; and 

 suppose these powers, for the sake of illustration, are equal 

 to 100, if they could be expressed in figures. Now, sup- 

 pose we put this ram to a ewe of a different character, 

 one that has been cross-bred, or bred without any care or 

 system, — very much as our native sheep or our common 

 cattle have been bred. She has, of course, far less heredi- 

 tary power, far less fixity of type and strength of blood, as 

 we say. Her hereditary power may be represented, we will 

 suppose, by 60. The result would be a lamb possessing very 

 much the same characteristics as the ram, because we have 



