122 GENETICS 



2. Some pairs of inherited characters follow the rules 

 of distribution of two or more different pairs of autosomes, 

 in the following particulars: 



(a) One member of each pair goes into each germ cell. 



(b) The members of the different pairs are distributed 

 to the germ cells independently, so that all possible com- 

 binations containing one member of each pair are formed 

 with equal frequency. 



(c) Each type of gamete from one parent unites with 

 each type from the other parent, the different matings being 

 equally frequent. 



3. These methods of distribution result, for the char- 

 acters manifested in the F^ generation, in certain typical 

 numerical proportions or ratios, known as Mendelian 

 ratios. 



4. This method of inheritance is known as Mendelism, 

 or Mendelian Inheritance. The rules of Mendelism are the 

 result of the rules of distribution of pairs of autosomes. 



5. Most characteristics of organisms are inherited in 

 this way; many more than are inherited in the sex-linked 

 manner. This is evidently because there is but a single pair 

 of X-chromosomes, while there are several or many pairs 

 of autosomes. 



6. Thus it is clear that among the different individuals 

 of a species, there are many different types of autosomes 

 (as there are different types of X-chromosomes), produc- 

 ing many kinds of characteristics. 



Other matters connected with autosomes will be taken 

 up in later chapters. 



The Y-Chromosome 



There remains another chromosome, not included In the 

 autosomes: namely the Y-chromosome. Has this functions 



