474 THE JOURNAL OF GEOLOGY. 



hung in the wind to dry. The water in which we washed them 

 usually remained as pure and empty as if it had been filtered, and 

 we often returned from our touring expeditions without even a 

 copepod or a zoea or a pluteus. 



The absence of the floating larvae is most remarkable, for the 

 sounds swarm with bottom animals which give birth every day 

 to millions of swimming larvae. The mangrove swamps and the 

 rocky shores are fairly alive with crabs carrying eggs at all stages 

 of development, and the boat passes over great black patches of 

 sea-urchins crowded together by thousands. The number of 

 animals engaged in laying their eggs or hatching their young is 

 infinite, yet we rarely captured any larvae in the tow net, and 

 most of these we did find were well advanced and nearly through 

 their larval life. 



It is often said that the water of coral sounds is too full of 

 lime to be inhabited by the animals of the open ocean, but this 

 is a mistake, for the water is perfectly fit for supporting the most 

 delicate and sensitive animals, and those which we caught 

 outside lived in the house in water from the sounds better than in 

 any other place where I ever tried to keep them, and instead of 

 being injurious, the pure water of coral sounds is peculiarly favor- 

 able for use in aquaria for surface animals. 



The scarcity of floating organisms can have only one explana- 

 tion. They are eaten up, and competition for food is so fierce 

 that nearly every organism which is swept in by the tide and 

 nearly every larva which is born in the sounds is snatched by 

 the tentacles around some hungry mouth. 



Nothing could illustrate the fierceness of the struggle for 

 food among the animals on a crowded sea-bottom more vividly 

 than the emptiness of the water in coral sounds where the bottom 

 is practically one enormous mouth. The only larvae which have 

 much chance to establish themselves for life are those which are 

 so fortunate as to be swept out into the open ocean where they 

 can complete their larval life under the milder competition of 

 the pelagic fauna, and while it is usually stated that the larvae 

 of bottom animals have retained the pelagic habit for the purpose 



