LIFE ON THE EARTH. 31 



high importance, by adopting means, if we may so 

 speak, to express the ideas which are prevalent in 

 another division. Though each great type seems to 

 have in a general sense one mam destiny marked out 

 for it by structure, place of residence, and habits, yet 

 each of the three higher types (Mollusca, Articulata, 

 Vertebrata) admits of modifications to suit some of 

 them for watery, and others for aerial life ; some for 

 swimming, others for flying, some for climbing, 

 others for burrowing into earth or wood or mud or 

 stone. Thus every thing that lives, is especially con- 

 structed for its life 1 , in conformity with general types 

 which admit of much modification, to suit particular 

 purposes. 



ADAPTATIONS OF LIFE STEUCTUEE. 



Some idea may be formed of the rich variety of 

 adaptations of animal structures to the conditions 

 under which they are appointed to live by a mere 

 enumeration of a few well-known cases, such as the 

 following variations in respect of the powers of 

 attachment or locomotion. 



Life in water is maintained in objects which 

 exhibit a vast diversity of forms and magnitudes, and 



1 La moindre facette d'os, la moindre apophyse a un carac- 

 tere determine, relatif a la classe, a 1'ordre, au genre et a Pespece 

 auxquels elle appartient. Cuvier, Ossemens Fossiles, Disc. prel. 



