Studies on variation and selection. 



By Arend. L. Hagedootn, Ph. Dr. and ISIrs. A. C. Hagedoorn, Med. Arts. 

 (Eingegangen: ii. September 1913.) 



Contents. 



page 



I. Unit-characters and dominance 145 



II. Continuous and discontinuous variation 151 



III. Selection in genotypically homogeneous groups of organisms 155 



IV. Statistical methods in the sudy of variation 171 



V. Series of genetic factors which influence the development in the same direction 173 



VI. Rules and Laws in Genetics 181 



I. Unit- characters and dominance. 



The qualities, characters, of any object, any organism, are all 

 that at any time can be known about this object or organism. Is it 

 possible to conceive of any part of this whole, of different characters 

 separately? Can we count an organism's characters, is it thinkable 

 that an organism has a definite number of characters? And what 

 would be the definition of "character"? 



To begin with tliis last question, it is clear, that, if one word 

 only should be undefinable, it would be "character". For definition is 

 naming a thing's qualities, and it is impossible to do this for the term 

 "character", for that genera,! thing, wliich all characters must have 

 in common, for that, which justifies the common name "character". 



It is obvious, that at every single stage of its development, a 

 developing plant or animal has its characters. It can hardly be said 

 that it "develops its characters". It develops its tissues and organs, 

 changing its qualities continually. This development of tissues and 

 organs we know to be caused and directed by a great number of 

 developmental factors, genetic ones (genes), and non-genetic ones. 



For purposes of description and classification, it is always 

 necessary to compare a given organism to others, first with an eye 

 to one organ or proportion between organs, next in another point. 



Induktive Abstammungs- und Vererbungslehre. XI, lO 



