ii THE METAZOA 75 



recognised as belonging to one or other of these great 

 phyla. A Prawn, a Crab, a Bluebottle Fly, a Spider, 

 are all formed on the same general plan as the Lobster : 

 they are jointed animals with jointed limbs, and have 

 the internal organs occupying similar positions with relation 

 to one another. They are all members of the phylum 

 Arthropoda. Again, a Mussel, a Snail, a Squid, are all 

 to be set side by side with the Oyster as conforming to 

 the same general type of structure; they are all members 

 of the phylum Mollusca. A Dog, a Lizard, a Fowl, again, 

 are obviously nearer the Fish : they all have skull and back- 

 bone, brain and spinal cord, and two pairs of limbs ; they 

 are all members of the great group Chordata. 



Altogether twelve phyla are to be recognised, viz. : 



I. Protozoa VII. Molluscoida 



II. Port/era VIII. Echinodermata 



III. Cceknterata IX. Annulata 



IV. Platyhelminthes X. Arthropoda 

 V. Nemathelminthes XI. Mollusca 



VI. Trochelminthes XII. Chordata 



