542 



THE AMERICAN NATURALIST [Vol. LII 



V 



Having indicated some of the difficulties existing along 

 the lines of established research in the efforts to account 

 for the derivation of the fundamental heritable units 

 making up an organism and having presented a series of 

 observations suggesting that a new perspective may be 

 obtained by utilizing methods of attacking the problem 

 somewhat different from those hitherto employed, the 

 particular purpose of the paper is accomplished. 



It may be asserted by some that such an attempt at a 

 summary disposal of the existing evidence as to the actual 

 origin of characters represents an unfortunate type of 

 destructive criticism. Furthermore, that the acceptance 

 of the validity of the arguments as to the long predeter- 

 mined nature of the genes or subgenes, leads us once 

 more in the direction of the somewhat antiquated theory 

 of preformation. It is not impossible that these views 

 are in part justified. Nevertheless it is well within the 

 bounds of propriety to occasionally inquire as to whether 

 the enthusiasm developed for a special discovery has 

 not resulted in too broad an application of its principles. 

 The mutation theory particularly as developed by Mor- 

 gan is of interest. It is circumscribed at least in part 

 by the phenomena of mendelian inheritance, and it is 

 evident that one should look farther for the facts which 

 may assist in explaining the real origin of the diversity 

 of living things. 



If additional studies support the view suggested by the 

 facts here presented, namely, that characters of a physio- 

 logical nature may be produced by environmental causes, 

 and that these in turn may demand the correlation of 

 morphological characters regardless of the origin of the 

 latter, an important step will have been made in account- 

 ing for the primary differentiation of organisms. The 

 later secondary differentiation through the combinations 

 of units which have thus arisen, and which attains its 

 maximum in the complex multicellular animals and 

 plants, offers no particular difficulties in its explanation. 



