Selection of Paramoecia. 



Jennings^ isolated from a population of Faramacia 

 eight races of Pure Lines, and his results confirm those of 

 Johannsen. 



Selection of Leptinotarsa. , , 



Tower 's2 results in breeding experiments with races 

 of Leptinotarsa 10-lineata are also in agreement with Jo- 

 hannsen's. Dark and light colored variations appeared in 

 the same Pure Line. When dark males and females were 

 mated the progeny were not dark, but fluctuated about 

 the average of the Pure Line, even after twelve generations 

 of such mating. 



Pure Lines and Mendelism.— It is now known (see pages 

 81-88) that the Fi generation of a Mendelian crossing all pro- 

 geny are hybrid, in the Fo generation half are hybrid and 

 half are pure regarding any particular character. In the F3 

 generation only one fourth are hybrid in the case of self- 

 fertilizing plants, and in the F4 generation only one-eight 

 are hybrid. In other words a self-fertilizing population 

 soon becomes composed of a number of pure lines, a 

 result which has been verified by experimenters. 



Chapter 13— TYPES OF BISEXUAL INHERITANCE 



With regard to Bisexual Inheritance three types may 

 be distinguished: 



1. Blended Inheritance,^ where there appears to be a 

 fusion of two characters when brought together in trans- 

 mission. As examples we have the familiar cases of the 

 blending of colors in mulattos, in horses, in cattle, in stature 

 of man, and perhaps in prepotency. 



2. Mosaic or Particulate Inheritance, where the char- 

 acters are separately expressed in different parts of the 

 same organ or system. Common examples are found in 

 piebald horses, cattle, and dogs. 



3. Alternate or Exclusive Inheritance, where the char- 

 acter of one parent is expressed apparently to the complete 

 exclusion of that of the other. Examples are found in 



(1) — Dr. H. S. Jennings (1868- ), Professor of Zoology. University 



of Pennsylvania, was educated at the Universities of Michigan, 

 Harvard, and Jena. He is recognized as the foremo.st investiga- 

 tor of the behavior of organisms. 



(2) — Dr. W. L. Tower (1872- ), of the University of Chicago, was 



educated at Harvard and Chicago. His studies on the evolution 

 of chrysomelid beetles and the development of coloration in in- 

 sects are masterpieces. 



(3) — Galton drew a distinction between Blended and Particulate In- 

 heritance, but regarded all inheritance as "largely, if not wholly, 

 particulate." 



74 



