CHIEF DIVISIONS OF THE ANIMAL KINGDOM. 45 



animal, no amount of complexity, no specialisation of organis- 

 ation, can raise the former above the latter. The one may be 

 the result of the high evolution of a low morphological type, 

 the other may be the result of the low evolution of a higher 

 morphological type, but the superiority of the ground-plan 

 gives the latter the higher place. We must therefore abandon 

 the idea that it is possible to establish a linear classification of 

 the animal kingdom. 



The following synoptical table gives briefly the leading 

 divisions of the animal kingdom, and the chief characters of 

 these : 



TABULAR VIEW OF THE CHIEF DIVISIONS OF THE 

 ANIMAL KINGDOM. 



INVERTEBRATE ANIMALS. 



SUB-KINGDOM I. PROTOZOA. 



Animal simple or forming colonies, usually very minute ; the body com- 

 posed of the structureless, jelly-like, albuminous substance called "sar- 

 code ; " not divided into regular segments ; having no nervous system ; no 

 regular circulatory system ; usually no mouth ; no definite body-cavity or 

 digestive system, or at most but a short gullet. 



CLASS A. GREGARINID^E. Minute Protozoa which inhabit the interior 

 of insects and other animals, and which have not the power of throwing 

 out prolongations of their substance (pseudopodia). No mouth. 



CLASS B. RHIZOPODA (Root-footed Protozoa). Protozoa which are 

 simple or compound, and have the power of throwing out and retracting 

 prolongations of the body-substance (the so-called "pseudopodia"). No 

 mouth, in most, if not in all. 



Order i. Monera. Ex. Protogenes. 



Order 2. Amcebea. Ex. Proteus Animalcule (Amceba). 



Order 3. Foraminifera. Ex. Lagena, Nodosaria, Globigerina. 



Order 4. Radiolaria. Ex. Thalassicolla, Polycystina. 



Order 5. Spongida. Ex. Fresh-water Sponge (Spongilla), Venus's 

 Flower-Basket (Euplectella). 



CLASS C. INFUSORIA (Infusorian Animalcules). Protozoa with a mouth 

 and short gullet ; destitute of the power of emitting pseudopodia ; furnished 

 with vibratile cilia or contractile filaments ; the body usually composed of 

 three distinct layers. 



Order i. Ciliata. Ex. Bell-animalcule (Vorticella), Paramcecium. 



Order 2. Flagellala. Ex. Peranema. 



Order 3. Suctoria. Ex. Podophyra. 



SUB-KINGDOM II.CCELENTERATA. 



Animals whose alimentary canal communicates freely with the general 

 cavity of the body ; body composed essentially of two layers or membranes, 

 an outer layer or " ectoderm," and an inner layer or "endoderm." No 

 circulatory system or heart, and in most no nervous system. Skin fur- 

 nished with minute stinging organs or "thread-cells." Distinct reproduc- 

 tive organs in all. 



CLASS A. HYDROZOA. Walls of the digestive sac not separated from 



