io6 The Insides and the Wordings of Living Things 



organs in their development and in their structure, yet both 

 make possible some kind of *' seeing." The feelers of certain 

 insects and our ears are so different in their development and 

 so different in their structure that nobody could mistake one 

 for the other. Yet both serve their owners in perceiving 



Ichthyosaurus 



Porpoise 



Fig. 31. Convergent Adaptation of Form 



The general form of an animal is frequently related to the 

 conditions under which it lives rather than to more funda- 

 mental characteristics. The modern mammal, porpoise, and the 

 ancient reptile, ichtyosaurus, have the outward form of a 

 "fish." After Osborn. 



" sound." The egg of a bird is totally unlike the seed of a 

 radish, yet both are alike in the function of starting a new 

 individual life. Analogies are to be found not only between 

 one type of animal and another, but also between plants and 

 animals. Since all living things have in common the neces- 

 sity of meeting certain conditions in the environment, all of 



