CHAPTER VIII 



MENDELISM 

 I.— HISTORICAL. 



A GREAT number of experiments on the effects of crossings 

 of plants and animals had been made by the old school of 

 hybridists, but without any definite outstanding result. 

 It was reserved for an Austrian Abbot, Gregor Johann 

 Mendel, to make one of the most fundamental discoveries 

 in the whole field of Heredity. Mendel, who had under- 

 taken a most laborious and prolonged series of hybridization 

 experiments in the garden of his monastery, chiefly on the 

 edible pea (Pisum sativum) and Hieracium, was enabled to 

 formulate a law of inheritance of these hybrids which bids 

 fair to become one of the corner-stones of the whole science 

 of Heredity. The subject of his paper, published as far back 

 as 1866 in a small provincial journal, passed unnoticed, 

 and had been wellnigh forgotten, when it was rediscovered 

 independently in the year 1900 by the botanists De Vries, 

 Correns, and Tschermak. Since then Mendel's experiments 

 have frequently been repeated and found to be correct, and 

 his ideas have been extended to many fields of inquiry. 

 Mendelism, as this branch of study has aptly been called, 

 has, in fact, become one of the most important and valuable 

 factors in our knowledge of inheritance, 



II. —MENDEL'S LAW. 



When two kinds of the edible pea {Pisum sativum) are 

 crossed with each other, one producing yellow seeds, the 



120 



