CONCLUDING WORDS. 249 



accumulating slowly but surely at the bottom of so many 

 seas. Should those ocean beds ever be elevated so as to 

 form dry land, their surface rocks will consist of chalk 

 similar to that formins: the famous cliffs of Dover. Insisr- 

 nificant as these creatures are, they are thus contributing, 

 and that in no small degree, to the building up of future 

 continents, — the homes, it may be, of different though not 

 altogether dissimilar animals to those we have just been 

 describing as at present in possession of 



THE TEMPERATE ZONES OF THE WORLD. 



