CHAPTER XIV 

 GENERAL CONSIDERATIONS AND CONCLUSIONS 



IN the preceding chapters certain matters had to be taken for 

 granted, since it was not possible, or desirable, at the time to discuss 

 more fully some of the terms that are in common use, or to analyze 

 more completely many of the phenomena. It was also not necessary 

 to give the general point of view under which the phenomena were 

 considered in their physical, chemical, or even causal connection. 

 Little harm has, I trust, been done by relegating such questions to 

 the final chapter. An attempt will now be made to give more explicit 

 statements in regard to the use and meaning of such terms as " organi- 

 zation," " polarity," " factors," " formative forces," " vitalistic " and 

 "mechanical principles," "adaptation," etc. 



It will be found that the hypotheses that have been advanced to 

 account for the phenomena of development and of regeneration may 

 be roughly classified under two heads : first, those in which the organi- 

 zation is " explained " as the result of the collective action of smaller 

 units ; and second, those in which the organization is itself regarded 

 as a single unit that controls the parts. Let us examine these points 

 of view more in detail, in order to see what has been meant in each 

 case by "the organization." 



A favorite method of biological speculation in the last forty years 

 has been to refer the properties of the organism to invisible units, 

 and to explain the action of the organism as the resultant of their 

 behavior. The hypothesis of atoms and of molecules, by means of 

 which the chemist accounts for his reactions, has proved so exceed- 

 ingly, fruitful as a working hypothesis that it has had, I think, a 

 profound influence on the mind of many biologists, who have, con- 

 sciously or unconsciously, attempted to apply a similar conception 

 to the structure of living organisms. The discovery that all of the 

 higher organisms are made up of smaller units, the cells, and that 

 the lower organisms are single, isolated cells, comparable to those 

 that make up the higher forms, has also drawn attention to the idea 

 that the whole organism is the result of the action of its units. Fur- 

 thermore, within the cells themselves units of a lower order have also 

 been discovered, such, for instance, as the chromosomes, the chloro- 



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