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The limits of this paper will not permit elaborate definitions, or fine 

 discriminations, and I have therefore to ask that you will kindly make 

 your own definitions, taking care to give to my words in general, the 

 narrowest sense compatible with the use to which I apply them. 



From the creatures and the plants, that man has domesticated for 

 his use, we have learned nearly all of the lessons in heridity, which we 

 have no good reason to unlearn, and m\- first illustration shall be from 

 one of these, the barn yard fowl. 



If we mate a Black Spanish fowl with a Buff Cochin, and hatch out 

 the eggs as the bees do theirs, in an incubator, till we have a hundred 

 chicks, among these we shall find a very great diversity. Some when 

 f ally grown will be nearly, if not quite as heavy as the Buff Cochin, and 

 some will weigh little, if any, more than the Black Spanish. Their re- 

 spective weights will probably vary between those natural to their se.x in 

 the two varieties to which their progenitors belong, but much the larger 

 number will be very nearly halfway between. And as color is not neces- 

 sarily correlated with weight, it is quite possible that the heaviest chick 

 will be the blackest; that is to say, that he may take his color almost en- 

 tirely from one parent, and his weight and form from the other. In color 

 every one of tne hundred chicks will, w^hen fully grown, be in some de- 

 gree distinguished from every other; and if we take color, size and form 

 together for our guide, there will not be one among the whole number 

 that we cannot readily distinguish from every other. Now this particular 

 cross from the great difference in size, form and color of the parent stock 

 enables us to see very clearly a fact which the closest and most careful in- 

 vestigation shows to be a general law It is this: 



All offspring are variable by heridity. And under some circu/iis/ances 

 the variations are ivide. 



Nearly every youth, who has amused himself with an aquarium, 

 knows that he can dwarf his fish if he chooses to do so. Other things 

 being equal, the weight of a fish depends upon the amount of food it is 

 allowed to consume. This variability is so great among fishes, that of 

 two as nearly alike as possible, either one may be fed so that he shall ex- 

 ceed a pound in weight, before the other, receiving very little food, shall 

 turn the scale at an ounce. 



Thus insufficiency of food affects the development of all organs. 

 Ail breeders of animals have some knowledge of this fact as applied to 

 their own business, and of which our fish merely affords a striking ex- 

 ample. It is an inevitable deduction, that when the food is of the general 

 quality which is suitable for the due nourishment of all the organs but is 

 insufficient in amount, the stronger organs, if such there be, will take 



