GLOSSARY 239 



Proglottid: a tapeworm segment. 



Prosoma: the primitive head of annehds made up of the prostomium and 

 the metastomium. 



Prostate gland: the gland which secretes the fluid in which the sperma- 

 tozoa are suspended. 



Prostomium: the anterior portion of the head of annelids. 



Pro thorax: the first thoracic segment in insects. 



Protopodite : the basal segment of a crustacean's leg. 



Protractor muscle: a muscle which extends the organ to which it is 

 attached or moves it forward. 



Proximal : a position toward the point of attachment — opposed to distal. 



Pseudopodium: a retractile process in rhizopods. 



Pulsating vacuole : a globule of excretory fluid in many protozoans. 



Pulvillus : an adhesive pad on the foot of insects. 



Pupa: the stage in the life of a holometabolic insect when it is undergoing 

 its metamorphosis. 



Pyrenoids: protein bodies in Euglena producing starch. 



Racemose vesicles: minute diverticula of the ring canal in starfishes. 

 Radial symmetry: having the parts or organs arranged symmetrically 



about a common center. 

 Radial tubes: a portion of the gastrovascular space in the medusa. 

 Radula: the band of calcareous teeth in the pharynx of gastropods and 



cephalopods. 

 Ray: one of the main divisions of the radiate body of echinoderms. 

 Receptaculum seminis: a receptacle for sperm in the female animal. 

 Rectum: the posterior division of the digestive tract. 

 Respiratory tree : a branched diverticulum of the rectum in holothurians. 

 Retractor muscles: muscles which draw in an organ to which they are 



attached. 

 Rostrum: a projection of the carapace in crustaceans. 



Sagittal: pertaining to a median dorsoventral plane in an animal's body. 

 Salivary glands : digestive glands at the anterior end of the digestive tract. 

 Scaphognathite : the elongated epipodite of the second maxilla in certain 



crustaceans. 

 Sclerite: a small plate forming a portion of the cuticula of a segment 



in insects. 

 Scolex: the anterior end of a tapeworm. 

 Scutellum: a small sclerite in the tergum of the thoracic segments in 



insects. 

 Segment: one of a number of serial divisions of an animal's body or of 



an organ. 

 Septum: a plate forming a division wall between two spaces. 



