MODERN THEORIES OF HEREDITY. 381 



being dominant and sugary recessive. In an experiment, 5,310 

 starchy (smooth) grains and 1,765 sugary (wrinkled) grains 

 were obtained in the F.2 generation. In both these cases we 

 have not got anything new, but if we combine the two cases just 

 considered, that is, take parents differing from one another in 

 tzvo characters, we are able to get the two characters combined 

 in a new way. For instance, crov> a " smooth yellow " mealie 

 with a " wrinkled white '" one. F.i is found to be " smooth 

 yellow." In an experiment in which the hybrid was pollinated 

 with "wrinkled white" pollen, the result was as follows: — 



Smooth yellow, seeds . . . . 2,869 \ 



Smooth white, seeds . . . . 2.q-?^ ' • .1 r- 



\A' • 1 1 J 11 J ^ - b - ui tlie 1*. 2 generation. 



\\ rmkled yellow, seeds . . 2,798 | * 



Wrinkled white, seeds . . 2.803 • 



that is, approximately equal numbers of the four possible com- 

 binations are obtained, of which the second and third did not 

 exist before in the parents. If the hybrid is self-pollinated we 

 get m F.2 a proportion of 9 smooth yellow grains, 3 wrinkled 

 yellow, 3 smooth white, i wrinkled white. All the wrinkled 

 whites breed true, but only i in 9 of the smooth yellow, and i in 

 3 of the other two classes. Of the remamder, 2 of the smooth 

 yellow are pure for the smooth character only, 2 others for the 

 yellow character only, while 4 are hybrid in both respects ; 

 2 wrinkled yellows give wrinkled yellow and wrinkled white ; 

 2 smooth whites give smooth white and wrinkled white. 



Gregor Mendel was born in 1822, and from 1853 to 1868 he 

 was a teacher of natural science in Briinn (Austria), where he 

 was a priest in the Augustine monastery. During those years 

 he worked on cross-breeding experiments with peas and other 

 plants. In peas he found seven pairs of characters behaving in 

 crosses exactly as those described above in the mealie. Amongst 

 these were : — 



Smooth (dominant'i and wrinkled (recessive) seeds. 

 Yellow (D) and green (R) cotyledons. 

 Grey (D) and colourless (R't-testas. 

 Inflated (D) and soft (R) pods. 

 Tall (D) and dwarf (R) stems. 



Mendel published the results of his experiments on peas in 

 1865, but they remained unknown to the world at large until 

 1900, when they were brought to light independently by dc Vries 

 and two other botanists. The facts first discovered by him and 

 many similar ones have been repeatedly investigated during the 

 last ten years, and there can be no doubt of their accuracy. 

 There is only one theory which exactly fits these facts, and that 

 is the one proposed by Mendel, and which, together with the 

 facts upon which it is based, is called *' Mendelism." This theory 



