CHAPTER LII. 



THE THEORY OF ORGANIC DEVELOPMENT. 



WE have learned something about the different kinds of matter, 

 and of the forms under which they appear; and we have studied 

 the forces acting upon matter, and the laws in accordance with 

 which they are supposed to act. In this study we have learned 

 that the molecular or atomic theory of matter, the law of defi- 

 nite proportions in chemical combinations, the undulatory the- 

 ory of light and heat, the conservation of energy, and the theory 

 of universal gravitation, are the great propositions or theories 

 which determine the lines of scientific thought, and around which 

 all the varied phenomena of the material world cluster for corre- 

 lation and explanation. These theories may not stand the test 

 of future investigation; they may prove inadequate, may be 

 modified, may give place to others; but at present they are the 

 best the only working theories we have and through them 

 most of the activities of nature around us may be explained ; 

 hence, some knowledge of them is valuable in any system of 

 education. 



We have studied the different forms of life which occur on the 

 earth. In them we found matter under the influence of a new 

 force, displaying quite a different cycle of events. A group of 

 molecules, endowed with life, comes into existence, is developed to 

 maturity , reproduces its kind, and dies. The history of life forms, 

 as individuals, is simply this and nothing more all their en- 

 ergies are directed toward growth and reproduction. Primarily, 

 their relations are to parents on the one side, and to offspring on 

 the other; incidentally, they have a wide range of relations with 

 other forms of life, and with the inorganic world. Living beings 

 differ widely in form, structure, and intelligence, and in many re- 

 spects the phenomena of life are more interesting than those of 



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