CHAPTER XIV 



THE INDIVIDUAL AS A MEMBER OF A RACE 



We have thus far been primarily concerned with the processes that enable 

 the organism to maintain itself as an individual. Much of any organism's 

 structure and behavior are understandable, however, only when we 

 examine its relationships to other individuals. One of the most essential 

 of such relationships is that any individual organism is only a temporary 

 unit in a sequence of generations. Each individual has a definitely limited 

 period of existence. This may be as brief as several days or weeks for the 

 individuals of some species, as much as "three score and ten" years or 

 more for man, or even several centuries for a few kinds of long-lived trees. 

 But in time the individual will cease to exist. The race to which the 

 individual belongs, however, continues through countless generations, so 

 that closely similar individuals successively appear, maintain themselves 

 for a period, and then die — to be replaced by new individuals of the same 

 kind. Here we encounter a new set of questions about organisms: How 

 are these successive generations produced? Why and to what extent are 

 the individuals of each new generation like those of the generation that 

 preceded them? How is the organism's existence as an individual related 

 to its membership in a race? 



THE DISCARDED THEORY OF SPONTANEOUS GENERATION 



Our modern concept of the origin and development of individual 

 organisms is much more recent than our knowledge of their structure. 

 At a time when a fairly accurate account of gross mammalian structure 

 was being written (by Galen in a.d. 200), nearly all educated men were 

 still willing to believe that most or many forms of life could arise spon- 

 taneously from nonliving matter. Frogs and insects were thought to come 

 from mud, bees from the decaying bodies of oxen, such household vermin 

 as mice and cockroaches from refuse. Even the wild geese (which breed 

 in the then unknown arctic regions) were thought to be formed from a 

 certain type of barnacle (still called the goose barnacle) that has a shape 

 suggesting the form of a goose. Ovid, who lived during the reign of the 



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