38 THE VOYAGE OF H.M.S. CHALLENGER. 



seawards of those forms which have occupied a continuous series of successive belts from 

 the shore, virtually ceases ; and that in the succeeding belt where the influence of the 

 climate of the region, derived from solar heat or from surface currents, is nearly lost, the 



Fig. 16. —RosscUa re?f(fe(, Wy. T, A He,xactinellid Sponge (natural size). 



number of animal species is at least greatly reduced. It has now been shown that an 

 cntii-ely azoic belt does not exist. 



The distri])ution of the fauna of shallow water depends, like that of the land, chiefly 



