26 INTRODUCTION TO ZOOLOGY. 



2d, — That in the Pacific and Indian oceans are tracts 

 where a gradual subsidence of the bottom of the sea is 

 going on ; and. 



3d, — That the Polypes work most efficiently at the 

 outer edge of the reef, where the water is the purest and 

 best aerated, and where their food is most abundant. 



To enter into further details upon this subject would 

 here be out of place. But this brief notice of the labours of 

 Coral -building Polypes cannot receive a more appropriate 

 close than that which has been furnished by the poet :— 



' Millions of millions thus, from age to age, 



With simplest skill and toil unweariable. 



No moment and no movement unimproved. 



Laid line on line, on terrace terrace spread, 



To swell the heightening, brightening, gradual mound. 



By marvellous structure climbing tow'rd the day. 

 )Each wrought alone, yet all together Wfrought. 



Unconscious, not unworthy instruments. 



By which a hand invisible veas rearing 



A new creation in the secret deep. 



Omnipotence wrought in them, with them, by them; 



Hence what Omnipotence alone could do 



Worms did. 1 saw the living pile ascend, 



The mausoleum of its architects, 



Still dying upwards as their labours closed : 



Slime the material, but the slime was turned 



To adamant by their petrific touch ; 



Frail were their frames, ephemeral their lives, 



Their masonry imperishable." — Montgomeuy's Pelican Isr..*ND 



of unfathomable depth. But if, according to My. Darwin's theory, the 

 polypes began originally to build at moderate depths, and the founda- 

 tions of their structure were gradually carried downwards by the pro- 

 longed subsidence of the bottom of the sea, it is obvious, from his state- 

 ments, that the ceaseless labours of the polypes are capable, in the 

 lapse of time,of producing all the phenomena described. Vide Darwin's 

 interesting work on the Structure and Distribution of Coral Reefs, 

 aud an able analysis of his theory in Lyell's Principles of Geol., voliii. 





Fig. 14. — aii.\ A.\EUOM£. 



