180 THE MICROSCOPIST. 



microscopist numerous specimens, but the details will be 

 best understood from the following chapter. 



As the classification of the Invertebrata is subject to 

 great variation, the following table, after Nicholson, is 

 added for the sake of comparison : 



INVERTEBRATE ANIMALS. 



SUB-KINGDOM I. PROTOZOA. 



CLASS I. GREGARINIDJE. Parasitic Protozoa, destitute 

 of a mouth, and destitute of pseudopodia. Ex., Gregarina. 



CLASS II. RHIZOPODA. Simple or compound ; destitute 

 of a mouth ; capable of putting forth pseudopodia. 



CLASS III. INFUSORIA. Generally with a mouth ; no 

 pseudopodia ; with vibratile cilia or contractile filaments. 



SUB-KINGDOM II. CCELENTERATA. 



CLASS I. HYDROZOA. Walls of the digestive sac not 

 separated from those of the body cavity ; reproductive 

 organs external. 



Sub-class 1. Hydroida. Ex., Hydra. Tubularia (pipe- 

 coralline). Sertularia (sea-fir). 



Sub-class 2. Siphonophora. Ex., Diphyes. Physalia 

 (Portuguese man-of-war). 



Sub-class 3. Discophora. Ex., Naked-eyed Medusae, or 

 Jelly-fish. 



Sub-class 4. Lucernarida. Ex., Sea-nettles, or " Hidden- 

 eyed " Medusae. 



CLASS II. ACTINOZOA. Digestive sac distinct from the 

 general cavity, but opening into it ; reproductive organs 

 internal. 



Order 1. Zoantharia. Ex., Sea- Anemones (Actinia). 

 Reef-building corals. 



Order 2. Alcyonaria. Ex., Sea-pen. Red coral. 



Order 3. Ctenophora. Ex., Cestum (Venus's girdle). 



