INTRODUCTION AND CLASSIFICATION 95 
From the foregoing it will be seen that the following 
sub-kingdoms are referred to :— 
(a) Coelenterata, comprising Sponges and Corals. 
(b) Echinodermata, comprising Sea-Urchins and Starfish. 
(c) Vermes or Worms. 
(d) Mollusea, including Snails and Shellfish. 
(e) Arthropoda, or animals whose bodies are furnished 
with jointed appendages. The Arthropoda are divided 
into two sub-branches, viz., Branchiata, or those which 
breathe by means of gills, and Tracheata, or those which 
breathe by means of trachez or air-tubes. The former 
(Branchiata) are again divided into two classes, one of 
which, the Crustacea, includes Crabs, Crayfish, ete. The 
latter (Tracheata) are divided into three classes, wz., 
Myriopoda (centipedes and millepedes), Arachnida (spiders), 
and Insecta (insects). 
Sub-Kingdom : Arthropoda. 
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Sub-Branch: Branchiata. Tracheata. 
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Class : _ Crustacea. Myriopoda. Arachnida. Insecta. 
(f) Vertebrata, divided into the following classes :— 
(1) Pisces (fish). 
(2) Amphibia (frogs, ete.) 
(3) Reptilia (lizards, ete.) 
(4) Aves (birds). 
(5) Mammalia (rabbits, ete.) 
The student will have a clearer idea of this classification, 
‘which has been made as simple as possible, by considering — 
the place in the animal kingdom occupied by each of the 
following life-forms :— 
