416 GLOSSARY. 



Parthenogenesis— The production of offspring from unfertilised eggs 



— i. e. from virgin mothers. 

 Pecten — A bivalve Mollusc — the Scallop. 

 Pedicellaria — A curious organ — perhaps a parasite — found growing 



round the spines on the skin of the Starfish. When magnified it 



looks like a pair of pincers. 

 Pedicellina — A Polyzoon. 

 PLANARiiE— 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. 

 POLYZOA — A class of animals long held t6 be Polypes, which externally 



most of them resemble ; now ranged under the head of Molluscs. 



They are also called Bryozoa, especially by foreign writers. 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 

 calcareous ; 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 Tiinicata, which floats in the open sea, 

 and produces offspring chained as it were together. 



Serpulje — 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 formei'ly supposed to be an ani- 

 malcule. Experiments have proved that without spermatozoa no 

 fertilisation takes place ; but that spermatozoa separated from the 

 fimd suflSce. 



Spicula — Fine-pointed bodies like needles. 



Terebella — 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 eg^. 



