THE SCHOOL OF THE SHORE 35 



on which some animals browse, such as the 

 Pellucid Limpet (Helcion pellucidwn), well 

 known for its beautiful blue-marked shell. 

 Some animals that look as if they were eating 

 the seaweed are feeding on microscopic plants 

 on the surface of the fronds. Along with the 

 seaweeds we must take the sea-grass, Zostera, 

 a flowering plant very abundant in some shore 

 waters. (2) There is, secondly, the result of 

 the breaking down of seaweeds and sea-grass, 

 the vegetable debris, the plant-dust. (3) There 

 is, thirdly, the multitude of minute free-swim- 

 ming and free-floating plants, such as Diatoms 

 and Desmids. These are exceedingly abundant 

 in near-shore waters, and get swept out to form 

 Open-Sea Plankton. The shore-waters serve as 

 a nursery for the Open Sea abundance of minute 

 plants. (4) There are the minute free-swim- 

 ming animals, some of which are hardly dis- 

 tinguishable from plants. (5) There is the 

 material, both animal and vegetable, brought 

 down from inland by rivers and streams, some- 

 times helped by the wind. We are not includ- 

 ing the mineral matter brought down which 

 serves to feed the shore plants. (6) There is 

 the jetsam brought in from the sea, for the 

 receding tide sometimes leaves on the beach 



