174 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



There simply is an " adaptation ' of structure in such 

 a sense in all the cases we have mentioned. We can say 

 neither more nor less. Granted that one of the outside 

 factors which comes into account is merely a necessary 

 " means " : then why is the histological consequence of the 

 presence of the means an actual adaptation to it as far 

 as its relation to functioning is concerned why is the 

 consequence of its absence also an adaptation to this absence 

 in its relation to functioning ? Why, to complete the series, 

 is the degree of the consequence of its presence an adapta- 

 tion to the degree of its presence ? 



All these relationships, which are so many facts, have 

 been absolutely overlooked by those who have been pleased 

 to deny morphological adaptation to functional changes 

 from without. 



To do full justice to them we may speak of " primary ' 

 regulative adaptations in all the cases mentioned above, 

 applying the word " primary," just as was done with regard 

 to restitutions, to the fact that there is some sort of 

 regulation in the normal connection of processes. We 

 reserve the title of " secondary adaptations " for cases such 

 as those described, for instance, by Vochting, 1 where not 

 merely one and the same tissue originates adaptively with 

 regard to the degree of its normal functioning, but where 



1 Vochting (Jahrb. wiss. Bot. 34, 1899) forced the bulbs of plants to 

 become parts of the stem, and parts of the stem to form bulbs ; in both cases 

 the most characteristic changes in histology could be observed, being in part 

 adaptations, but in part restitutions of the proper type. (See also my 

 Organische Regulationen, 1901, p. 84.) A true and simple instance of a 

 "secondary adaptation" seems to be furnished in a case described by 

 Boirivant. In Robinia all the leaflets of a leaf-stalk were cut off : the leaf- 

 stalk itself then changed its structure in order to assist assimilation, and also 

 formed real stomata. 



