An Introduction to a Biology 



and which are not. And it would seem, in general, that 

 Mendelian characters are to be found amongst the contents 

 of the retort and are not exhibited by the retort itself. 



II 



NOTES OF A LECTURE GIVEN IN JULY, 1914, AT THE 

 GRADUATE SCHOOL OP AGRICULTURE, HELD AT THE 

 UNIVERSITY OF MISSOURI, COLUMBIA, MISSOURI 1 



THERE is a fundamental difference between character of 

 species and character of varieties. 



According to De Vries a varietal character is one which 

 may be borne by any plant or animal. A species character 

 must be borne by all individuals. 



Character of a species is the ensemble of characters and 

 something unique. 



It is like a man's written signature. A varietal character 

 is like a stamped signature. It may be stamped over a large 

 number of individuals. 



Varietal characters are all that will be possible of isola- 

 tion as unit factors ; e.g. wrinkledness of peas is also stamped 

 on corn : it is not a species character. 



De Vries thinks varietal characters are Mendelian. Prob- 

 ably Mendelian characters are varietal characters. 



Four general conclusions with reference to Mendelian 

 results ; 



(1) Time is no factor. 



(2) Nothing is obtained that is not put in. 



(3) Varietal characters are unit factors. 



(4) Mathematical expressions can be applied to Men- 



delian phenomena. 

 Has time anything to do with the fixation of a character ? 



Experiment with peas to test this. 



There are two varieties of pea-flower in regard to colour : 

 the white pea-flower (the commonest) and the pink pea- 



' Vide supra, Preface, p. xvii. 

 IOO 



