210 THE CONTINUITY OF THE RACE 



It is also clear that once the chain of continuing generations is broken, 

 the race will cease to exist. Actually this has happened for many thou- 

 sands of kinds of organisms in the past and will continue to happen to 

 many races in the future. The organisms that exist today are members 

 of biologically successful races : some of the individuals of each generation 

 of each race were able to maintain their own normal span of existence 

 and to reproduce still another generation to carry on in turn. 



In our study of the individual as a member of a race, it will be more 

 profitable to look at organisms in general than to confine our attention 

 to one or a few, as we did in the preceding section. We shall see that 

 the reproductive processes of one organism will often help in the inter- 

 pretation and understanding of similar but outwardly different processes 

 of other forms. In the more than a million different kinds of individuals 

 and races of organisms, with their great differences in size, complexity, 

 and type of organization, we should expect to and do find great differences 

 in the details of reproductive methods and adaptations. If we confine 

 our attention to the common and essential processes, however, we find 

 that all reproductive methods may be classified into a relatively small 

 number of different types. These various types and processes of repro- 

 duction form the subject matter of the following three chapters. 



