CORRESPONDENCE BETWEEN LIFE AND ITS CIRCUMSTANCES. 73 



dition : instance, a lump of carbonate of soda that effervesces 

 when dropped into sulphuric acid ; a cord that contracts 

 when wetted ; a piece of bread that turns brown when held 

 near the fire. But in these cases, we do not see a connexion 

 between the changes undergone, and the preservation of the 

 things that undergo them ; or, to avoid any teleological im- 

 plication the changes have no apparent relations to future 

 external events which are sure or likely to take place. In 

 vital changes, however, such relations are manifest. Light 

 being necessary to vegetal life, we see in the action of a 

 plant which, when much shaded, grows towards the unshaded 

 side, an appropriateness which we should not see did it grow 

 otherwise. Evidently the proceeding of a spider, which 

 rushes out when its web is gently shaken and stays within 

 when the shaking is violent, conduce better to the obtainment 

 of food and the avoidance of danger than were they reversed. 

 The fact that we feel surprise when, as in the case of a bird fas- 

 cinated by a snake, the conduct tends towards self-destruction, 

 at once shows how generally we have observed an adaptation 

 of living changes to changes in surrounding circumstances. 



Note further the kindred truth, rendered so familiar by 

 infinite repetition that we forget its significance, that there 

 is invariably, and necessarily, a conformity between the vital 

 functions of any organism, and ttFe conditions in which it is 

 placed between the processes going on inside of it, and the 

 processes going on outside of it. We know that a fish can- 

 not live in air, or a man in water. An oak growing in the 

 ocean, and a seaweed on the top of a hill, are incredible 

 combinations of ideas. We find that every animal is limited 

 to a certain range of climate ; every plant to certain zones of 

 latitude and elevation. Of the marine flora and fauna, each 

 species is found exclusively between such and such depths. 

 Some blind creatures flourish only in dark caves ; the limpet 

 only where it is alternately covered and uncovered by the 

 tide ; the red-snow alga rarely elsewhere than in the arctic 

 regions or among alpine peaks. 



