46 INTRODUCTION. 



those of the general body-cavity, the two coinciding with one another. 

 Reproductive organs external. 



Sub-class I. HYDROIDA (Hydroid Zoophytes). 



Order I. Hydrida. Ex. Fresh- water Polype (Hydra). 

 Order 2. Corynida. Ex. Pipe-coralline (Tubularia). 

 Order 3. Sertularida. Ex. Sea-firs (Sertularia). 

 Sub-class II. SIPHONOPHORA (Oceanic Hydrozoa). 

 Order 4. Calycophorida. Ex. Diphyes. 



Order 5. Physophorida. Ex. Portuguese Man-of-War (Physalia). 

 Sub-class III. DISCOPHORA (Jelly-fish). 



Order 6. Medusida Ex. Trachynema. 

 Sub-class IV. LUCERNARIDA (Sea-blubbers). 

 Order 7. Lucernaridce. Ex. Lucernaria. 

 Order 8. Pelagidce. Ex. Pelagia. 

 Order 9. Rhizostomida. Ex. Rhizostoma. 

 Sub-class V. GRAPTOLITID^E (extinct). 



CLASS B. ACTINOZOA. Stomach opening below into the body-cavity, 

 which is divided into a number of compartments by a series of vertical par- 

 titions or " mesenteries." Reproductive organs internal. 



Order I. Zoantharia. Tentacles simply rounded, in multiples of 

 five or six. Ex. Sea-Anemones (Actinidae), Star- 

 corals (Astrseidse), Brain-corals (Meandrina), Madre- 

 pores (Madreporidse). 



Order 2. Alcyonaria. Tentacles fringed, in multiples of four. 

 Ex. Dead-man's-toes (Alcyonium), Organ-pipe Coral 

 (Tubipora), Sea-rods (Virgularia), Sea-pens (Penna- 

 tula), Red Coral (Corallium). 

 Order 3. Ritgosa (extinct). 



Order^ Ctenophora. Animal oceanic, swimming by means of 

 bands of cilia or " ctenophores." Ex. Pleurobrachia, 

 Venus's Girdle (Cestum). 



S US-KINGDOM III. A NNUL OIDA . 



Animals in which the alimentary canal is completely shut off from the 

 general cavity of the body, and in which there is a distinct nervous system. 

 A true blood-circulatory system may or may not be present. In all there 

 is a peculiar system of canals, which usually communicate with the exterior, 

 and which constitute what is called the "water- vascular system." The 

 body of the adult is never composed of a succession of definite rings, or pro- 

 vided with successive pairs of appendages disposed symmetrically on the 

 two sides of the body. 



The Annuloida are divided into two great classes : 



A. ECHINODERMATA. Integument composed of numerous calcareous 

 plates joined together, or leathery and having grains, spines, or tubercles 

 of calcareous matter developed in it. Water-vascular system (ambulacral 

 system) mostly employed in locomotion, and generally communicating with 

 the exterior. Adult generally more or less starlike or "radiate " in shape ; 

 young mostly showing more or less complete "bilateral symmetry," that is, 

 showing similar parts on the two sides of the body. Nervous system 

 radiate. 



Order I. Crinoidea (Sea-lilies). Ex. Feather-star (Comatula), Me- 

 dusa-head Crinoid (Pentacrinus), Stone-lily (Encri- 

 nus.) 



Order 2. Blastoidea (extinct). 

 Order 3. Cystoidea (extinct). 



