ONE-CELLED ANIMALS. 



25e 



belong Red Coral {Coralliwin rubrum), and the reef- 

 biiilding corals (Astrcea, Mceandrina, etc.). 3. The 

 Sponges (Porifera), which are usually considered 

 ccelenterates, though they possess no nettling organs 

 (Freshwater Sponge = Spongilla, Bath Sponge = Eu- 

 spongia officinalis). 



Seventh Sub-Kingdom : PROTOZOA 



(One-celled Animals). 



This sub-kingdom includes animals which are mostly 

 microscopic, or at any rate small, and live in the sea, 

 fresh water, or damp places. They are unicellular, 

 and consist of a soft viscous substance (protoplasm 



Fig. 149. — Two species of Proteus Animalcule (Amcsba)^ one with protoplasmic 

 ■processes, slender and branched ; the other with short blunt processes. Highly 

 magnified. 



or sarcode) of contractile nature, and therefore capable 

 of altering its shape. They may or may not be 

 enclosed by a firm wall. Many secrete siliceous 



