ADAPTATION 175 



a profound disturbance of all functioning connections, due 

 to the removal of portions of the organisation, is followed 

 by histological changes at absolutely abnormal localities ; 

 that is, where a real change of the kind of functioning is 

 the consequence of the adaptation. It, of course, will be 

 found very difficult to discriminate such phenomena from 

 real restitutions, though logically there exists a very sharp 

 line between them. 



A few more concrete instances may now close this 

 account of adaptation to functional changes coming from 

 without. Though almost all the adaptive characters in 

 the aquatic forms of amphibious plants represent a less 

 complicated state of organisation than the corresponding 

 structures in their terrestrial forms, and therefore have 

 wrongly been regarded as simply due to a stopping of 

 morphogenesis for want of necessary means, yet there are 

 a few of them that are positive complications in comparison 

 with the land-forms : the so-called aerenchyme, especially 

 well developed in the water-form of Jussiaea is such an 

 instance. This tissue stands in the direct service of 

 respiration, which is more difficult to be accomplished under 

 water than ordinarily, and represents a true adaptation to 

 the altered function. 



Among animals there is only one well-studied instance 

 of our first type of adaptive morphological characters. 

 Salamandra atra, the black salamander, a species which only 

 inhabits regions at least two thousand feet above sea-level, 

 does not bring forth its young until metamorphosis has 

 taken place. The larvae, however, may be removed from 

 the mother's body at an earlier stage and forced to complete 

 their development in water. Under these circumstances, 



