CHAPTER XIII 



FACTORS IN ONTOGENY AND EXPERIMENTAL 



DEVELOPMENT 



Many biologists find their greatest triumph in the doctrine that the 

 living body is a "mere machine/' but a machine is a collocation of 

 matter and energy working for an end, not a spinning toy, and when 

 the n\'ing machine is compared to the products of human art the 

 legitimate deduction is that it is not merely a spinning eddy in a 

 stream of dead matter and mechanical energy, but a little garden in 

 the physical wilderness. 



What the distinction (between vital and nonvital) may mean in 

 ultimate analysis, I know no more than Aristotle or Huxley, nor do 

 I believe that anyone will know until we find out. — Brooks. 



While in the foregoing chapter there is outlined in some 

 detail the general facts and processes and so-called "laws'' of 

 ontogenetic development, ^ve purposely omitted any reference 

 to what is known or guessed concerning the causes and control 

 of this development. Only less wonderful than life itself is 

 the unfolding and changing of a single tiny apparently homo- 

 geneous speck of life substance (a fertilized egg cell), into a 

 great myriad-celled, extraordinarily heterogeneous, but per- 

 fectly organized fully developed plant or animal body. And 

 only second in point of insistence to man's queries about the 

 Avhence and whither of life itself are his demands to be informed 

 concerning the causes and control of development. It is indeed 

 strongly felt by most biologists that the study of development, 

 that is, the study of the initiating and guiding factors of de- 

 velopment, is more likely to reveal to us the basic factors and 

 mechanism of evolution than any other kind of study. It is 

 plain that evolution, its causes and method, are intimately 

 bound up with the general primary phenomena of life, as 



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