CONCLUSIONS AND SUGGESTIONS 203 



The process of inheritance is involved to exactly 

 the same extent in the reconstitutional development 

 of a new individual from a piece of Tuhularia stem or 

 of the planarian body, or in the formation of a new grow- 

 ing tip from the differentiated cells of a leaf (Figs. 38, 39), 

 from callus tissue (Fig. 40), or from any other part of 

 the plant, as it is in the reproduction of a new individual 

 from the egg, with or without fertilization, in any of 

 these forms. The simple agamic and experimental re- 

 productions, moreover, afford very much greater pos- 

 sibilities for the analysis and control of the processes 

 and mechanism of inheritance and develoj^ment than 

 gametic reproduction. Any adequate conception of in- 

 heritance and development must be based upon ana- 

 lytic investigation of these simple reproductions and 

 synthesis of the results, and it must interpret inheritance 

 in gametic reproduction in terms of the simpler processes. 

 Continued sexual breeding and hybridization under 

 controlled conditions and with pedigreed individuals has 

 contributed much and undoubtedly will contribute 

 further toward the solution of certain special problems 

 of inheritance, and also affords results which possess a 

 statistical value, but this method of procedure alone 

 can never carry us very far toward the solution of the 

 fundamental problem of inheritance. The key to this 

 problem also will be found in the simpler reproductive 

 processes. 



If the organism is a unit in inheritance and develop- 

 ment we must expect to find that so-called "acquired 

 characters" may be impressed on the organism to such 

 a degree that sooner or later the reaction system may 

 give rise to these characters without the action of the 



