76 EFFECTS OF ADAPTATION sec. 



offspring of these striped and unstriped parents are again 

 striped or unstriped — in spite of constant crossing (pammixis) 

 these two forms appear everywhere side by side with no con- 

 necting forms between them. 



If everything were adapted, there would be no characters 

 at present useless, representing either rudiments of formerly 

 useful or the besfinningfs of new characters. There would be 

 no gradual transitions, and, more particularly, no change of 

 function, and also there would be no correlative char- 

 acters — there could be no striking variability in forms 

 at all. 



The universal dominion of adaptation is finally also con- 

 tradicted by the reflection, that from the given materials only 

 instruments of a certain quality can be produced in organic 

 nature^ — that these instruments might be many times better 

 for their purpose, more perfect, less easily damaged — that they 

 are not in all cases completely adapted to the requirements 

 seems to me beyond a doubt. 



Nevertheless, what great importance, in spite of my refusal 

 to recognise its exclusive dominion, I ascribe to adaptation in 

 the modification of forms will be best gathered from the 

 section on the adaptation of lizards. 



It was not my purpose in this place to exhaust the question 

 of non-essential characters, as it is discussed elsewhere in this 

 work, both in preceding and following pages. I wished 

 merely to mention here the existence of such characters as an 

 argument against the assumption that adaptation rules ex- 

 clusively in all cases. 



If this exclusive dominion did belong to it, if everything 



1 Compare here my remarks, reproduced in a later passage, on the formation 

 of sense-organs, in my monograph Die Medusen, anatomisch und jjhysiologisch 

 auf ihr N erven- system untersuchf, Tiibingen. Laupp, 1878. I there showed how 

 clearly the structure of sense-organs, especially of the optic and auditory organs 

 of various animals, indicated that the given material permits only the formation 

 of instruments constructed on certain few principles, which instruments satisfy 

 the requirements, but are obviously often very imperfect. 



