546 TEE POPULAR SCIENCE MONTHLY 



zoologist, though less acquainted than might be wished with com- 

 mercial breeding. 



Another paper was entitled, " Mendel's Law in Relation to Animal 

 Breeding," and a third, " Heredity in the Light of Recent Investiga- 

 tions." 



In the 1907 session of the same body, Mr. Spillman, of the Depart- 

 ment of Agriculture, in a paper entitled, " The Chromosome in the 

 Transmission of Hereditary Characters," said : " I believe that it will 

 finally be possible to work out the complete relation so that we can get 

 a full understanding of the behavior of hereditary characters and thus 

 breed for improved forms with almost as much certainty as the chemist 

 miies solutions in order to produce a desired compound." At the same 

 time and place. Dr. Davenport, of the Carnegie Institution of Wash- 

 ington, used these words : " Indeed, the fact that the enzymes of the 

 germ cells, and particularly of the egg, determine hereditary char- 

 acters, points the way to the modification of hereditary qualities and 

 to the production of this or that character at will." 



The expectations of such sanguine persons have not been realized. 

 Considerable progress has been made, but it has been and bids fair to 

 be more in the nature of a steady march than of a sudden flight. 



Those who were most hopeful of the sufficiency of Mendelism over- 

 looked three things : that we are not able to originate any specific char- 

 acter desired ; that not all characters are transmitted in accordance with 

 the Mendelian formula; and that, except for purposes of research, it is 

 seldom practicable to breed for but one single or unit character at a 

 time. Approved animal form embraces probably innumerable unit 

 characters. So far, the only definitely known Mendelian unit char- 

 acters in large animals are superficial ones, such as coat characters, 

 which are of no direct commercial importance. The relation of the 

 vital body characters is not understood and no capacity for useful func- 

 tions has been shown to be a unit character. Even with the low num- 

 ber of three or four useful unit characters known to be Mendelian, the 

 chance of their being combined in a single individual is so small as to 

 be of no interest to a practical breeder. 



The difficulties of perpetuating a character according to Mendel's 

 law are much less serious with plants than with animals. Knowing 

 that there is strong probability of a unit character of a plant's being 

 Mendelian, the certainty regarding the rate at which it may be propa- 

 gated adds greatly to the attractiveness of plant breeding and greatly 

 stimulates the search for and endeavor to produce valuable variations. 



The Breeders and Mendel's Law 

 Mendelism has, therefore, given considerable immediate aid to eco- 

 nomic plant breeding. It has served to interest seed growers in biology 



