5M MANUAL OF ELEMENTARY ZOOLOGY 



Phylum CCELENTERATA, 



Radially symmetrical, diploblastic animals. The 

 most important members of this group are : 

 Class Hydrozoa. 



Polyps and medusas with ectodermal gonads 

 and no vertical partitions in the enteron. 

 e.g. Hydra, Obelia. 

 Class Scyphozoa (Acaleph/e). 



Medusas with endodermal gonads and with a 

 gullet and vertical partitions in the enteron 

 of the polyp stage when the latter exists, 

 e.g. Aurelia. 

 Class Anthozoa. 



Polyps without a medusoid generation and 

 with endodermal gonads, a gullet, and 

 vertical partitions in the enteron. 



Here belong Sea Anemones and Corals. 

 B. Grade Triploblastica. 



Metazoa in whose bodies a third layer, the meso- 

 derm, lies between ectoderm and endo- 

 derm and usually contains spaces known 

 as the haemoccele and ccelom. 

 i. Phylum Platyhelminthes. 



Flat, worm-like Triploblastica without anus, 

 blood vessels,' or (in the adult at least) 

 body cavity, with an excretory system 

 formed of branched tubes ending in flame 

 cells, and with a complicated, usually herma- 

 phrodite system of reproductive organs. 



a. Class Turbellaria. 



Free-living, ciliated Platyhelminthes. 

 e.g. Planaria. 



b. Class Trematoda. 



Parasitic Platyhelminthes with a cuticle, a 

 forked gut, and no proglottides, 

 e.g. Distomum, Schistostomum. 



c. Class Cestoda. 



Parasitic Platyhelminthes with a cuticle, no 

 gut, and proglottides which break off from 

 the body, 

 e.g. Tccnia. 



