NATURE AND CAUSES OF ADAPTATIONS. 69 



•ill Avatei-. Some ])lanis are liairv in drv localities, but are nearly 

 naked in humid districts. Others (i-eat these direct responses to 

 extei-nal conditions under the heading:: of accommodation, and reserve 

 the word adajjtation for characters which api>ear regularly in a spe- 

 cies or variety, but which fit it for some special condition, such as 

 that ])resented to the cotton plant by the boll weevil. It has seemed 

 ])roper, therefore, to discuss as protective adaptations any characters 

 which seem to give the Central American varieties an advantage in 

 withstanding the attacks of the w^eevil, particularly if it can be shown 

 also that the presence of the weevil would tend to the preservation 

 and extension of the given character. 



In the strict sense of the words, the weevil-resisting adaptations 

 of the cotton plant would include only those characters which have 

 been increased by the selective influence of the boll weevil, but in the 

 broader practical sense we may treat as a weevil-resisting adaptation 

 any feature which tends to limit the destructiveness of the insect. 



The adaptive nature of some of the characters of the Central 

 American varieties discussed in the present paper is reasonably obvi- 

 ous, but in other instances extended studies in developmental biology 

 and primitive agriculture might be necessary to determine the origin 

 and development of a varietal characteristic which may have signifi- 

 cance in the weevil problem. 



It is easy to understand that so injurious an insect as the boll weevil 

 has exerted a definite selective influence ever since its remote ances- 

 tors turned their attention to the cotton. Perhaps its earlier food 

 plants were completely exterminated. The nearest living relatives 

 of the cotton are the species of Hibiscus, Paritium, and Thespesia, 

 none of which is known to have any attractions for the weevil. It is 

 evident, too, that in the presence of the weevil the cotton plant would 

 have met long ago a like fate if it had not been able to take on its 

 various adaptive characters. That so many of the features by which 

 it differs from its nearest relatives have such obvious connection with 

 the weevil would certainly justify the belief that strong adaptive 

 influence had been at work, even if the other circumstances were 

 unknown. 



In thinking of the relation between two organisms like the weevil 

 and the cotton we often fall into the error of too threat humanizinir. 

 so to speak; that is, we ascribe too great intelligence or too complete 

 a reaction to cause or conditions. Thus the weevil, althou"-h hishh- 

 specialized in some of its instincts, has, of course, no equivalent for 

 the human judgment. It will puncture, as already seen, buds much 

 too small to raise a larva, and will lay its eggs in the rind of the boll, 

 where the larva^ can never develop. If the conditions are too favor- 

 able to the weevil, as in humid regions, it would undoubtedlv exter- 



