GLOSSARY. 401 



Pedicellina— A Polyzoon. 



Planari.e — Flat worms without segments, mostly parasitic, abundant in 



ponds and on sea-weed. 

 Pleurobranchus — A gasteropodous mollusc, with its gill hanging down from 



the side. 

 POLTZOA — A class of animals long held to be Polypes, which externally most 



of them resemble ; now ranged under the head of Molluscs. They are also 



called Bri/ozoa, especially by foreign writei-s. The Plumatella (Frontispiece, 



fig. 1) is a Polyzoon. 

 Pycnogonid^ — Small crustaceans, mostly parasitic. 



Sabella — One of the worms which live in tubes ; but its tube is not cal- 

 careous ; it is formed of mud or particles of sand glued together. 



Sagitta — An animal not yet classed. (See p. '251, and Plate V., fig. 2.) 



Salpa — A mollusc, of the order Tunicata, which floats in the open sea, and 

 produces offspring chained as it were together. 



SerpuLuE — Worms which live in calcareous tubes secreted from their own 

 bodies. In the water they expand lovely feathery gills. 



Spermatozoon — A microscopic filament, forming the essential part of the 

 fertilising fluid of animals, and formerly supposed to be an animalcule. 

 Experiments have proved that without ^spermatozoa no fertilisation takes 

 place ; but that spermatozoa separated from the fluid suffice. 



Spicula — Fine-pointed bodies like needles. 



Tebebella —A worm living in a tube of sand or shells glued together by 



an exudation from its body. (Plate VII.) 

 Troglodytes — Cave-dwellers : a species of Sea Anemone. 



Venusta — A species of Sea Anemone : orange-disked. 

 Vitellus— The yolk of the egg. 



6) 



