o 



1 6 BIOLOGY AND ITS MAKERS 



of the pea, but not visible. When peas of different color 

 were cross-fertilized, one color would be stronger apparently 

 than the other, and would stand out in the hybrids. This 

 was called the dominant color. The other, which was held 

 in abeyance, was called recessive; for, though unseen, it was 

 still present within the young seeds. That the recessive 

 color was not blotted out was clearly sho\\Ti by raising a 

 crop from the hybrid, a condition under which they would 

 produce seeds like those of the two original forms, and in 

 equal number; and thereafter the descendants of these peas 

 would breed true. This so-called purity of the germ-cells, 

 then, may be expressed in this way: ''The hybrid, whatever 

 its own character, produces ripe germ-cells, which produce 

 only the pure character of one parent or of the other" 

 (Castle). 



Although Mendel's discovery was for a long time over- 

 looked, happily the facts were re-discovered, and at the 

 present time extensive experiments are being made with 

 animals to test this law: experiments in the inheritance of 

 poultry, the inheritance of fur in guinea-pigs, of erectness 

 in the ears of rabbits, etc., etc. In this country the experi- 

 ments of Castle, Davenport, and others with animals tend 

 to support Mendel's conclusion and lift it to the position of 

 a law. 



Rank of Mendel's Discovery. — The discovery by Mendel 

 of alternative inheritance will rank as one of the greatest 

 discoveries in the study of heredity. The fact that in cross- 

 breeding the parental qualities are not blended, but that they 

 retain their individuality in the offspring, has many possible 

 practical applications both in horticulture and in the breeding 

 of animals. The germ-cells of the hybrids have the dominant 

 and the recessive characters about equally divided; this will 

 appear in the progeny of the second generation, and the races, 

 when once separated, may be made to breed true. 



