CHAPTER II 

 BEPEODUCTION AMONG ANIMALS AND PLANTS 



IN order to obtain a proper orientation of the problem 

 of inbreeding and outbreeding, one must consider first 

 some of the general facts regarding reproduction among 

 animals and plants and their relation to inheritance. 



The significant changes in both kingdoms have been 

 remarkably similar. The differences are differences in de- 

 tail, and for this reason they are additional arguments in 

 favor of the idea that there are special advantages asso- 

 ciated with the coincidences found in the general processes 

 involved. For example, asexual propagation is more gen- 

 eral in the simpler, sexual reproduction in the higher or- 

 ganisms. But sexual reproduction in animals has largely 

 supplanted the asexual method, in plants sexual reproduc- 

 tion was merely added. Is this not evidence of an im- 

 portance to be attached to the sexual method, apart from 

 a simple provision for multiplication? Again, the diver- 

 sity of sex organs which has arisen among the various 

 groups of animals and plants is highly surprising, yet this 

 dissimilarity may be wholly of a superficial nature. When 

 examined solely with the object of inquiring what systems 

 of mating these variations entail, the parallelisms in each 

 history stand out impressively. If these facts be kept in 

 mind throughout the short discussion of heredity and re- 

 production which follow, their probable evolutionary sig- 

 nificance is not difficult to grasp ; but if the profusion of 

 variation in detail, or even the general mechanism of ac- 

 complishing a particular result is allowed to distract 

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