22 ZOOLOGY DIEECTIONS 



eral g'enera of but a single family spongillidae belonging to the 



ORDER SILICISPONGIAE. 



III. Phylum Coelenterata 



Nematocysts present. Polyp without ectodermal esophagus. 

 Solitary polyps without medusae or medusa buds 



CLASS HYDROZOA, ORDER HYDRARIAE 



IV. Phylum Plathelminthes 



1 Free-living' flatworms with body covered with cilia, class 



TURBELLARIA 2 



2 Digestive system with three main branches, one toward the 



head and two running posteriorly order tricladida 



V. Phyla Nematiielminthes and Annelida 



1 (4) Worms with cylindrical bodies, not segmented. Covered 



with cuticula. phylum nemathelminthes 2 



2 (3) A longitudinal lateral line on each side of body. Body 



usually tapering at one end class nematoda 



3 (2) Without lateral line. Adults live in water, larvae are 



parasitic in insects. Body practically uniform diameter 

 throughout class gordiacea 



4 (1) Body segmented, without jointed appendages, phylum 



ANNELIDA 5 



5 (6) Body with anterior and posterior suckers. Nearly al- 

 ways without setae class hirudinea 



6 (5) Setae present and regularly distributed around each 



segment class chaetopoda, subclass oligochaeta 



VI. Phylum Mollusca 



1 (2) Body without a distinct head, usually bilaterally sym- 

 metrical. Bivalve shell. Mantle bilobed class acephala 



