196 Regeneration 



tation. Either certain substances flow to the lowest 

 level and collecting there induce growth and possibly 

 changes in the character of growth (as in Antennularia) 

 or if the cells have elements of different specific gravity 

 the relative position of these elements may possibly 

 change and influence in this way the conditions for 

 growth. The influence of gravitation as well as of con- 

 tact upon life phenomena are at present little under- 

 stood. 



In all these cases v^f lieteromorphosis the original 

 form is not restored. It is needless to say that they are 

 incompatible with the theory of natural selection. 



The reader will have noticed that in this chapter one 

 term has not been mentioned which is commonly met 

 with in the literature, namely the "wound stimulus.'* 

 As the writer had indicated in a former publication,^ 

 the word "stimulus*' is generally used to disguise our 

 ignorance of (and also our lack of interest in) the causes 

 which underlie the phenomena which we investigate. 

 Regeneration very often does not take place near the 

 wound but at some distance from it. But even when 

 the regeneration takes place at the edge of the wound 

 the latter only serves to create conditions for regen- 

 eration, and these conditions cannot be expressed by 

 the word "stimulus." 



While our knowledge of the r61e of the whole in 



* Loeb, J., Die chemische Entwicklungserregung des tierischen Eies, 

 Berlin, 1909. 



