Ss6 CM. Child. 



science. It is necessary to recognize the interrelations of numerous 

 and widely different factors in all organic phenomena. I believe 

 that we have as yet no adequate conception of the complexity of 

 these phenomena. The universal desire to generalize results in 

 misleading schematization. The processes of organic nature 

 are even more varied than we suspect. 



SUMMARY. 



1. Anterior regeneration in regions anterior to the middle of 

 the ganglia is complete, and amount and rapidity of regeneration 

 are directly proportional to the size of the part removed. From 

 levels posterior to the middle of the ganglia regeneration is both 

 qualitatively and quantitatively incomplete, no head being re- 

 generated. In these cases the amount and rapidity of regenera- 

 tion are inversely proportional to the size of the part removed. 



2. Lateral regeneraion in the presence of the ganglia is com- 

 plete; in the absence of the ganglia it is complete except in the 

 lateral head-region and the amount and rapidity of regeneration 

 are directly proportional to the size of the part removed if the 

 piece is large. As the size of the piece is reduced the proportion 

 becomes inverse. 



3. As in the case of posterior regeneration, there is a close 

 parallelism between the rapidity, amount and completeness of 

 anterior and lateral regeneration and the characteristic motor 

 activity of the part concerned. 



4. The relation between the nervous system and regeneration 

 in Leptoplana may conceivably be either direct, in that nervous 

 stimuli themselves constitute formative factors, or indirect, in that 

 functional conditions resulting from use of the part in a particular 

 manner determined by its relation with the nervous system, are 

 the formative factors properly speaking. In the latter case the 

 formative factors may be either stimuli to growth and other changes 

 or they may be directly mechanical. The facts seem to indicate 

 that the relation is actually indirect except perhaps as regards the 

 regeneration of parts of the nervous system itself; the conditions 

 are both mechanical and non-mechanical but the former are 

 especially important in certain respects. 



