PHENOMENA AND PRINCIPLES OF BREEDING 467 



have as yet afforded no positive conclusions. The consensus of 

 opinion of breeders, based on general observation, is that prepotency 

 is transmitted, but it requires very careful analysis of the results 

 of breeding the progeny of prepotent individuals to show how far 

 such results are unusual in the sense that the results of breeding 

 from the prepotent individual were, and how far they should be 

 considered normal after the prepotent individual had raised the 

 average of its family or race. 



Present and latent characters. " Dominance " and " recessive- 

 ness " are terms used to describe the behavior of extreme, or plainly 

 distinct, grades of characters in sexual reproduction. While each of 

 the two germs which in this form of reproduction unite to form a 

 new organism brings to the new organism possibilities of develop- 

 ing any character of the body which produced it, it is manifestly 

 impossible that the new organism should develop with characters 

 in the aggregate equal to the sum of the characters of both parents. 

 It must be, as has been stated, a composite, in which the characters 

 of the parents blend, and usually blend very irregularly, presenting 

 all grades of blending between different forms of a character (as of 

 color or comb), or a variety of different combinations of characters. 



Alternate inheritance, reversion, and atavism. If organisms 

 reproducing sexually could transmit to their offspring only such 

 developments or modifications of characters as could be produced 

 direct from characters as developed in them, a character which had 

 once disappeared could not reappear, except as it might come from 

 some new combination. But it is found in practice that characters 

 disappearing in one generation often reappear in the next or, less 

 numerously, in later generations. The most familiar illustration of 

 such reappearance in characters of poultry is the perpetually recur- 

 ring single comb in rose-combed varieties. Similar " faults " occur 

 frequently in other characters in all varieties of poultry, cropping 

 out sometimes most unexpectedly in stock in which they have been 

 scrupulously avoided by the breeder for many generations when 

 making up his matings. The biologist, observing the phenomena 

 of reproduction in a short series of generations, and breeding to 

 secure full manifestation of the laws of inheritance, deals impartially 

 with characters. If a character can come back, he gives it every 

 opportunity to do so. He considers the character recessive, tending 



