CHAPTER XV 



INHERITANCE IN PROTOZOA 

 H. S. Jennings 



In his Genetics o'f the Protozoa (1929), the author has reviewed some- 

 what fully the investigations and literature on inheritance in Protozoa, 

 up to 1929. No attempt is made to repeat here these detailed reviews; 

 the plan is rather to summarize the present state of knowledge on the 

 subject. Very great advances have been made since 1929, particularly in 

 the knowledge of biparental inheritance, largely through the work of 

 Moewus (1932-38). 



The question dealt with in the study of inheritance is : To what extent 

 and how are the constitutions and characteristics of later genera- 

 tions affected by the constitutions of their ancestors, particularly by the 

 constitutions of the immediate parents? Certain subordinate questions 

 arise in connection with this : To what extent and how are characteristics 

 affected by environmental conditions.'* What are the relations between 

 environmental modifications and genetic constitution? 



By genetic constitution is meant the constitution insofar as it affects 

 descendants. The genetic constitution is known from studies of multi- 

 cellular organisms to be embodied in certain genetic materials. These 

 are, mainly or entirely, found in the chromosomes. General genetics has 

 shown ( 1 ) that in the chromosomes there are great numbers of diverse 

 genetic materials (known commonly as genes or factors), having dif- 

 ferent effects on development and characteristics; and (2) that genetic 

 materials are transferred bodily from parents to offspring. 



In the present account the term "factors" will usually be employed in 

 place of the term "genes," since the latter has acquired, of late, certain 

 doubtful theoretical implications. 



Genetic materials have two essential properties: (1) the genetic ma- 

 terials received from parents affect the development and characteristics 

 of the descendants; (2) the many different kinds of genetic materials 



