318 BIOLOGY AND ITS MAKERS 



Chance combinations of these germ-cells will yield on the 

 average, one union of dominant with dominant, one union of 

 recessive with recessive, and two combinations in which 

 dominant and recessive are united. In the latter instance the 

 dominant will be the visible character, the recessive, though 

 present, being invisible. This segregation of the gametes 

 into two sets of "pure" gametes was recognized by Mendel 

 in an attempted theoretical explanation of his observed facts, 

 and, in view of the state of knowledge at the time, showed 

 remarkable analytical ability. 



Mendel's papers were published in 1866 and 1867 in the 

 Proceedings of the Natural History Society of Briinn, but 

 their importance was overlooked for nearly thirty-five years. 

 The periodical in which they appeared was not widely known, 

 and moreover, the minds of naturalists at that time were 

 largely occupied with the questions of organic evolution 

 raised through the publications of Darwin. In the year 

 1900, however, the great principle of heredity worked out 

 by Mendel was independently re-discovered by the botanists 

 DeVries, Torrens, and Tschermak. By searching the litera- 

 ture for anticipations of their results, the unrecognized papers 

 of Mendel were brought to light and made generally known 

 to the scientific world. 



Since 1900, extensive experiments by Bateson and others 

 have served to confirm and extend Mendel's discovery. In 

 the United States the experiments of Davenport and Castle 

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

 of erectness of ears of rabbits, etc., as well as the experimental 

 work of others, has extended our knowledge of Mendelian 

 inheritance. The combined work on inheritance in animals 

 and plants of all observers has so thoroughly supported 

 Mendel's conclusions, that the principle of alternative in- 

 heritance is commonly spoken of as Mendel's law. 



Rank of Mendel's Discovery. The discovery by Mendel 



