INTEODUCTION. 



19 



Order 3. Turhellaria. — Ex. Planarians (Planaria), Ribbon-worms 



(Nemertes). 

 Order i. Acantkocephala (Thorn-headed worms). — Ex. Echino- 



rhynchus. 

 Order 5. Oordiacea (Hair-worms). — Ex. Gordius. 

 Order 6. Nemaioda (Thread-worms). — Ex. Round-worm (Ascaris), 



Guinea-worm (Filaria), Vinegar-eel (Anguillula). 

 Order *!. Rolifera (Wheel-animalcules). — Ex. Builder-animalcule 



(Melioerta), flexible Creeper (Notommata). 



SUB-KINGDOM IY.—Al<n<rjJLOSA. 



Animal composed of numerous definite segments or " somites," arranged 

 longitudinally, one behind the other. Nervous system always present, con- 

 sisting of a double chain of nervous masses, or ganglia, which are placed along 

 the lower surface of the body, and form a collar around the gullet. Limbs 

 (when present) turned toward that side of the body on which the main 

 masses of the nervous system are situated. 



Division A. Anaktheopoda. — Locomotive appendages, when present, 

 not distinctly jointed or articulated to the body. 



Class L Gephteea. — Ex. Spoon-worms (Sipunculus). 

 Class II. Annelida (Einged-worms). 



Order 1. Hirudinea. — Ex. Leeches (Sanguisuga, Hirudo). 



Order 2. Oligochmta. — Ex. Earth-worms (Lumbrious), Water-worms 



(Nais). 

 Order 3. Tiibicola. — Ex. Tube-worms (Serpula). 

 Order 4. Erranlia. — Ex. Sand-worms and Sea-centipedes (Nereis), 

 Lob-worm (Arenicola), Sea-mouse (Aphrodite). 

 Class III. Chjetognatha (Arrow-worms). — Ex. Sagitta. 

 Division B. Aethkopoda. — Locomotive appendages jointed or articu- 

 lated to the body. 



Class I. Crustacea. — Respiration aquatic, mostly by gills. Two pairs 

 of antennje. Limbs more than four pairs in number, carried upon the tho- 

 rax, and generally the abdomen also. 



Order 

 Order 

 Order 



Order 

 Order 

 Order 



Order 



Order 8. 



Order 9. 



Order 10. 



Order 11. 



Order 12. 



Order 13. 



Order 14. 



Class II. 



Water-fleas (Cypris). 

 Cyclops. 

 Branched-horned Water-fleas 



Brine-shrimp (Artemia). 



(Daph- 



Bliizocephala. — Ex. Peltogaster. 



IcMhyophthira. — Ex. Lemsea. 



Cirripedia. — Ex. Barnacles (Lepas), Acorn-shells (Bala- 



nus). 

 Oslracoda. — Ex. 

 Copepoda. — Ex. 

 Cladocera. — Ex. 



nia). 

 Fhyllopoda. — Ex. 

 Trilobita (extinct). 



Merostomata. — Ex. King-crabs (Limulus). 

 Zcemodipoda. — Ex. Whale-louse (Cyamus). 

 Isopoda. — Ex. Wood-lice (Oniscus), Slaters (Ligia). 

 Amphipoda. — Ex. Sandhopper (Talitrus), Fresh -water 



Shrimp (Gammarus). 

 Stomapoda. — Ex. Locust-shrimp (Squilla). 

 Decapoda. — Ex. Lobster (Homarus), Cray-fish (Astacus), 



Shrimps (Crangon) ; Hermit-crabs (Pagurus); Crabs 



(Cancer, Carcinus), Land-crabs (Gecarcinus). 

 AiiACBNiDA. — Respiration aerial, by pulmonary chambers or 



