204 CRUISE OF THE BARRERA 



to light a most astonishing number of creatures 

 that are not otherwise detected. A gallon or two 

 of strong solution of the blue salt is emptied into 

 the pool and results quickly follow. The fish 

 succumb at once and float to the surface gasping 

 for air. All mollusks emerge from beneath their 

 hiding-places and there is a general effort to leave 

 the pool. The wariest of cephalopods, the small 

 sneaking octopi, are forced to abandon their 

 caution and boldly expose themselves. Little 

 crustaceans that are practically invisible upon 

 algse or among the rocks, the color of which they 

 simulate, abandon their color fortresses. Holo- 

 thurians and echinoids appear from unsuspected 

 places, and worms with undulating motion swim 

 to the surface. It is a general stampede, quick 

 and nervous or slow and deliberate, according to 

 the nature of the beast. 



The tide pools yielded a remarkable catch of 

 about six hundred fish of fifty-seven species, many 

 being young of reef-dwellers, quantities of ophi- 

 urans and other echinoids, many mollusks includ- 

 ing the octopi, worms of many species, and a fine 

 lot of crustaceans representing several orders. A 

 good tropical tide pool, that is, one with abun- 



