206 



THREE CRUISES OF THE "BLAKE. 



concerned, they naturally procure their most abundant supply 

 of food within a comparatively short distance from land, where 

 all the detritus brought down by rivers, or formed by the action 



Fig. 129. — Zoea of Carcinus. 

 Greatly magnified. 



Fig. 130. — Panopus Embryo. 

 Greatly magnified. 



Fig. 131. — Zoea of Porcellana 



of the sea on the coast line, settles on the bottom around the 

 slope of the continental areas. The larger materials are left 

 close to the shores, and with increasing distance the detrital mat- 

 ter becomes smaller, till finally reduced to an impalpable ma- 

 terial or solids in solution it finds its way to the most distant 

 parts of the continental slopes, or is carried still farther by 

 oceanic currents skirtino* the shores. As I have shown in the 

 chapter on the Florida Reefs, the distribution of the deep-sea 

 fauna is really a question of food ; and we may expect to find it 

 most abundant upon the continental shelf, — along the lines to 

 which the greatest amount of detritus is carried by the incessant 

 action of the varied winds, tides, and currents to which the 

 sea-shore is exposed. 



