CHAPTER XII. 

 STRUCTURAL RELATIONSHIP. 



In the earliest Hebrew Scriptures we find living 

 things already separated, in the minds of the writers, 

 into such general classes as " grass, " "herb yielding seed," 

 "fruit trees yielding fruit after their kind, whose seed is 

 in itself," "creeping things," "fish," '"fowls of the air," 

 "beasts of the field," and "man," which enabled them 

 to be collectively mentioned, and paved the way for 

 future more precise groupings, To these writers, how- 

 ever, each kind was separately created and independent 

 of all others. 



Grecian philosophical speculation concerning the 

 origin of things found no satisfaction in the creation 

 hypothesis, and at an early date the idea prevailed that the 

 earth and its creatures arose in a more or less orderly se- 

 quence by process of evolution. With as much thorough- 

 ness as their familiarity with the living creatures per- 

 mitted, they divided them into groups suggesting the 

 order of descent, beginning with the most simple and 

 ending with the most complex. These endeavors were, 

 however, much impeded by superstitions regarding the 

 ready spontaneous generation of almost any living thing, 

 and the equally prevalent belief that living things of 

 one kind readily metamorphosed into others. 



The history of scientific classification seems to begin 

 with Aristotle, who as an anatomist and physiologist 

 acquired a broad knowledge of the lower animals and 

 divided them as follows: 



Bloodless Animals. Insects 

 Molluscs 

 Crustacea 

 Testacea 

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