THE SCHOOL OF THE SHORE 35 



weeds on which some animals browse, such as 

 the Pellucid Limpet (Helcion pellucidum], 

 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-swimming and free-floating plants, such 

 as Diatoms and Desmids. These are exceed- 

 ingly 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-swimming animals, some of 

 which are hardly distinguishable from plants. 

 (5) There is the material, both animal and 

 vegetable, brought down from inland by rivers 

 and streams, sometimes helped by the wind. 

 We are not including 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 



