DOCTRINE OF EVOLUTION AND RELATED IDEAS 



497 



primitive germ cells which are carried within. In what way 

 will these diverse complex chemical bodies influence one another 

 in the development of the organism ? Will they blend or will one 

 swamp or exclude the other ? If they blend, will they add their 

 tendencies; will they neutralize each other; or will their union 

 give rise to compounds so new as to carry qualities that neither 

 parent had? Or may all of these things happen with the 

 different qualities? These are the questions of heredity. 

 Only recently have we begun to get real statistical and breeding 

 data that will help us to answer them. 



492. Mendel's Experiments. — Gregor Mendel, an Austrian 

 monk, published in 1866 the results of breeding experiments 



Fig. 252. 

 TALL (pure) X DWARF 



TALL. . 

 (Hybrid) 



■ Fi 



self-bred 



TALL (3) 

 (i Pure : 2 Hybrids) 



DWARF (i)....F2 



i I I 



TALL 3 TALL . i Dwarf DWARF F3 



(all) (as in F2) (all) 



Fig. 252. Diagram illustrating Mendel's results in breeding tall and dwarf peas. Fi, Fs, Fj. 

 first, second, and third filial generations. The first generation are all tall; but we know they are 

 impure (hybrid) both because we know the parents, and by their offspring when bred among them- 

 selves. The dwarfs (recessive) when they once appear are necessarily pure, and breed true. The 

 tails of Fi generation are of two kinds as shown by their offspring, — i pure to 2 impure. The figures 

 in parenthesis indicate relative numbers. All generations after F. are self-bred. 



conducted by him, together with his interpretation of these. 

 His work was unknown until 1900. Since that time his facts 



32 



