DISTRIBUTION OF ANIMAL COMMUNITIES 15 



rivers and standing waters contain considerably more salts 

 (e.g. places like the Norfolk Broads or the meres of Lancashire 

 and Cheshire). Then there is a rather sudden increase in 

 the steepness of the gradient through brackish water lagoons 

 and estuaries to the sea itself. The sea, having been there 



Kllepora . ichotema 

 n. Iruncota 



Sxitnphytum hirhinv 

 S poimcSuJrk 



Heliopora corrulia. 

 Seriafopora. hyiOrix 



I 



ft}^ri|fOfiA23NE|''^)J'|^|A«OPORA 2DNE| SCLEROPHYTUM ZONE \8Q\UilR 



ZONES 



F • paUida. 

 Fav\tiii abdita 

 Coiioitnea pet^nafc, 

 Pavona dianai 

 P vca\a/is 



Montipcr* ranoio. 



M. hopida 



M. foliosa. 



Acropora .smifhi 



A. hOLfnA 



A qufteki 

 A 



pKaraoiuiipcijriKrftia 



Qofiopora. ttn^udtns 

 fbrt«4 froqOKX 



Hahwtdicn- »p 



LthetHunnvtn hrmo o-uJtoceo. 



i 



The thickness of the black stripes indicates the abundance of each species 

 at various distances from "the shore. 



Fig. 1. — Zonation of corals (together with a few calcareous algae) on a 

 reef in the New Hebrides, showing that the phenomenon of dominance 

 exists among corals, just as among plants. The left-hand side of the 

 diagram is the shore of the island, while the right-hand side is the outer 

 edge of the reef. (From Baker .^°*) 



much longer than the inland lakes and ponds, contains enor- 

 mously more salts than the latter, but really it is only one end 

 of a gradient which started high up in the mountains. There 

 are well-marked different associations of animals in all these 

 types of waters. Of course, other factors than salt content 



