lOO SEA AND LAND 



more highly organized animal creatures to enter on such 

 combinations in the open air. 



Another peculiarit)- in tlie environment of aquatic animals 

 depends on the capacity of water for floating substances. All 

 these forms on the land have to be endowed with the power 

 of moving that they may seek their food, but in the sea the 

 water floats the food to many waiting mouths, and the creat- 

 ures may dwell fixed to thc^ same place on the bottoni from 

 their birth to their death, waiting patiently for the currents to 

 bring thcMii their nourishment. All the corals and sponges, 

 and nearly half the mollusks, obtain their supply of food in 

 this manner; perhaps one-half of all the marine species trust 

 to this chance of gathering their aliment from the passing 

 water. 



For a century or more naturalists have known a great 

 deal concerninir the marine organisms which dwell in the 

 shallow water next the sliore. They long ago learned the 

 amazing richness of these littoral forms. The census of 

 species amounts now to more than one hundred thousand 

 distinct kinds ; it is, however, of late that tliey have ascer- 

 tained that the deeper parts of the ocean-floors have also an 

 abundant and varied ])eopling. Although the study of the 

 abysmal life of the seas is but just begun, and the knowledge 

 which has been gained is probably but a small part of that 

 which will be gathered during the coming years, the results 

 of the incpiiries, in many ways, are not only most interesting, 

 but in the highest degree important in shaping our views con- 

 cerning the origin and history of organic life. These creat- 

 ures of the abysmal regions of the ocean appear mainly to 

 have been derived, by a process of variation, from those 

 which once inhabited the shallower waters next the shore. 



