270 



A YEAR IN SCIENCE 



Permission of Field Museum of Natural History. 



Fig. 127. A group of marine animals; A, starfish; B, sea urchin; 

 C, coral ; D, sponge. 



walls of which are strengthened and supported by a 

 hard or horny substance. All except a very few of the 

 sponges live in the ocean. Most of the sponges which 



Permission of Field Museum of Natural History. 

 Fig. 128. Drying sponges, Key West, Florida. 



are used for commercial purposes come from off the 

 coast of Florida or from the -Mediterranean Sea. 



Protozoa. These are the simplest animals, and like 

 the simplest plants they consist of but a single cell. 

 They are found in any water, but are most abundant 

 in stagnant water. Many of them are so much like the 

 one celled plants that it is impossible to draw a sharp 

 line between them. All of the protozoa are very small, 



