CHAPTER XXXV. DIAGNOSTIC CHARACTERS OF THE 

 PRINCIPAL DIVISIONS OF THE ANIMAL KINGDOM. 



THE animal kingdom is first divided into a number of 

 subdivisions which are called sub-kingdoms or Phyla. 

 The latter term is now generally used, because it means a 

 tribe, or clan, or stock, and implies common descent among 

 the collection of organisms to which it is applied. The largest 

 and most important phyla are : the Protozoa or unicellular 

 animals ; the Porifera or sponges ; the Coelenterata, includ- 

 ing hydroids, jelly-fishes, corals, and sea-anemones ; the 

 Platyhelmia or flat- worms ; the Nemathelmia or thread- 

 worms; the Echinodermata, including star-fishes, sea- 

 urchins and their allies ; the Annelida or segmented worms ; 

 the Arthropoda or animals with jointed appendages, such as 

 Insects and Crustacea ; the Mollusca ; and the Chords ta, 

 which include the vertebrate animals. In the London 

 University Syllabus for the Intermediate Science Examina- 

 tion which comes into force in 1909, all these phyla are 

 mentioned except the following : Porifera, Nemathelmia, 

 Echinodermata, Mollusca. The Arthropoda, however, are 

 called the Articulata, the term used by Cuvier at the 

 beginning of the nineteenth century for one of the four prin- 

 cipal divisions of his classification ; this division included the 

 Annelida and the Arthropoda. It is not usual at the present 

 time to employ the term Articulata as synonymous with 

 Arthropoda. In the University Syllabus also the term 

 Chordata is used as distinct from and contrasting with the 

 Craniata, whereas it is generally understood to include the 

 latter, the primitive forms without cranium or vertebrae 

 being called Prochordata. 



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