MENDELISM 



By a. D. DARBISHIRE, M.A, 

 Demonstrator in Zoology, Royal College oj Science, London 



Perhaps the most interesting, certainly the most sensational, 

 chapter in the history of biology, when it comes to be written, 

 will be that which deals with the discovery of Mendel's papers 

 and with the fruit which that discovery has borne. We are 

 already in possession of all the material for the former topic ; 

 and the first instalment of the fruit which has already been 

 harvested augurs well for the quality of what is to come. 



In 1865, a man absolutely unknown to the biological world, 

 Gregor Johann Mendel, read before a meeting of the Natural 

 History Society of Briinn a paper on his experiments with 

 Peas, entitled " Experiments with Plant Hybrids." To-day no 

 name is better known to biologists than that of Mendel. And 

 yet, when he died in 1884, he was as obscure as when he read 

 his famous paper. Indeed, it was not until sixteen years after 

 his death that Mendel suddenly burst from obscurity into fame. 



In 1900 Mendel's experiments with Peas were repeated, and 

 his results confirmed, independently by De Vries in Amsterdam, 

 Correns in Leipzig, and Tschermak in Vienna. This spark — 

 the discovery of Mendel's paper — has been responsible for the 

 generation of an enormous amount of energy, which has mani- 

 fested itself ever since in a continually smouldering train of 

 investigation ; and on one or two occasions in explosions of 

 controversial violence. 



We must now make it our business to become familiar with the 

 facts which Mendel discovered, and with the interpretation which 

 he put upon them. Mendel found that varieties of the culinary 

 pea, Pisum sativum, could be classified according to a number 

 of constant, true-breeding characteristics, such as the form of 

 the plant, whether normal {i.e. tall) or dwarf; or such as the 

 colour of the cotyledons of the seeds, whether yellow or green ; 

 and so forth. 



Mendel crossed a Tall with a Dwarf. The resulting hybrid 



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