CLASSIFICATION OF ANIMALS 159 



Group comprising Amoeba, Euglena Paramecium, etc., upward of 10,000 



species Phylum Protozoa 



Group comprising sponges upward of 800 species 



Phylum Porifera. 

 Group comprising Hydra, sea-anemones, etc., upward of 3000 species 



Phylum Coelenterata 

 Group comprising comb-bearing jelly forms, upward of 500 species 



Phylum Ctenophora 

 Group comprising tape worm and flat worms, upward of 1600 species 



Phylum Platyhelminthes 

 Group comprising round worms, filaria, etc., upward of 1000 species 



Phylum Nemathelminthes 

 Group comprising ringed worms, earthworm types, upward of 2500 species 



Phylum Annelida 

 Group comprising lobster, crab, shrimp and allies, upward of 8000 species 



Phylum Crustacea 

 Group comprising insects breathing by tracheae, upward of 300,000 species 



Phylum Insecta 

 Group comprising centipedes, spiders, ticks, etc., upward of 5000 species 



Phylum Arachnida 

 Group comprising clams, snails and allies, upward of 22,000 species 



Phylum Mollusca 

 Group comprising star fish, sea cucumbers, etc., upward of 2500 species 



Phylum Echinodermata 



Group comprising fish, frogs, reptiles, birds, mammals, upward of 25,000 

 species. Phylum Vertebrata 



In addition to these there are several minor groups which are 

 recognized by biologists but in which the number of species is 

 comparatively small, here for example are the phyla Rotifera 

 (350 species), Polyzoa (700 species), Brachiopoda (100 species) 

 and Tunicata (300 species). 



No one has made an accurate enumeration of the existing 

 species of animals but it is safe to say that more than 350,000 

 species are known and grouped into distinct phyla. 



In each phylum, although the type is the same throughout, 

 the structures may be so modified as to give very distinct forms 

 of animals. Different types of vertebrates give the most fa- 

 miliar examples of this, mammals, birds, reptiles, amphibia and 

 fish being widely different from one another, yet all belong to the 

 same phylum. Birds, being fundamentally of one type, are 



