LIFE IN THE OCEAN CLARK 383 



On land the most successful plants are the flowering plants, which 

 grow by forming a series of units one above the other called phytons, 

 by the multiplication of these units producing a rosette of leaves 

 or a tall or branching leafy stem and thus exposing the maximum 

 green surface to the sunlight and the air. 



The sea water being charged with nutrient particles throughout, 

 it is obvious that in the shallow regions any animals which are able 

 to attach themselves and to produce in the same way as do the flower- 

 ing plants an indefinite series of reduplicated units each more or less 

 perfect in itself would be able to avail themselves to best advantage 

 of the food materials drifting here and there and all around about 

 them. 



Attached animals, particularly animals that grow and look like 

 plants, are especially characteristic of the sea shores. The so-called 

 colonial animals along the coasts which, plantlike in their growth 

 though in no other way, live firmly fastened and secure their food 

 from the restless water as it washes back and forth, are the sponges, 

 certain ccelenterates, including the hydroids, the corals, the sea 

 fans or gorgonians, the millepores, the sea pens or pennatulids, the 

 umbellularians, the alcyonarians, the antipatharians, the colonial 

 anemones, and some other types, the polyzoans, the phoronids, the 

 rhabdopleurids, the cephalodiscids, and the colonial tunicates or 

 sea squirts. 



The sponges, all of which when alive possess a strong odor dis- 

 agreeable to us, though it may be attractive to the little things on 

 which they live, have the general mass (it can scarcely be called a 

 body) pierced by numberless small holes leading into small tubes 

 lined with extremely delicate hairlike structures, called cilia, beating 

 inward. These small tubes lead into larger ones, and these finally 

 into an opening leading to the exterior, through which a constant 

 stream of water, impelled by the ceaseless action of the cilia in the 

 small tubes, pours outward. On its journey through the canals of 

 the sponge this water has lost a considerable portion of the nutritive 

 particles which originally it contained. One does not think of 

 muscular power in connection with the apparently motionless 

 sponges. Yet on the reefs at Bermuda at low tide I have frequently 

 seen the calm surface of the sea much agitated by a stream of water 

 coming from below which investigation showed originated from the 

 outlet of a large sponge. 



This food-collecting system of the sponges is very efficient, and 

 other animals take advantage of it. Jointed worms of many kinds, 

 one a much-branched creature with a head on the end of every branch, 

 live within the canals, as do various small crustaceans and brittle 

 stare. Barnacles, embedded in the outer layers, and some crustaceans 



