GLOSSARY 219 



Presternum : the ventral surface of the prothorax in insects ; wasp, 3 ; 

 grasshopper, 10. 



Prostomium : the anterior portion of the head of annelids, 62. 



Prothorax : the first thoracic segment in insects ; wasp, 2 ; grasshopper, 9. 



Protopodite : the basal segment of a crustacean's leg ; crayfish or lobster, 32. 



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

 attached ; Nereis, 64 ; mussel, 91. 



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



Pseudopodium : a retractile process in rhizopods, 194. 



Pulsating vacuole : a globule of excretory fluid in many protozoans ; Para- 

 mecium, 186 ; Vorticella, 189 ; Euglena, 193 ; Amoeba, 195. 



Pulvillus : an adhesive pad on the foot of insects ; fly, 8 ; grasshopper, 12. 



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

 its metamorphosis. 



Racemose vesicles : minute diverticula of the ring canal in starfishes, 146. 

 Radial symmetry : having the parts or organs arranged symmetrically 



about a common center. 

 Radial tubes : a portion of the gastro-vascular space in the medusa, 167, 



173, 175. 

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



cephalopods ; snail, 120 ; squid, 132. 

 Ray : one of the main divisions of the radiate body of echinoderms, 141, 



150, 155. 

 Receptaculum seminis : a receptacle for sperm in the female animal ; grass- 

 hopper, 16 ; spider, 27 ; crab, 44 ; snail, 118. 

 Rectal glands : glandular structures in the rectum of certain insects, 15. 

 Rectum : the posterior division of the digestive tract ; grasshopper, 15 ; 



caterpillar, 21 ; crayfish or lobster, 39 ; Bugula, 86 ; mussel, 96 ; clam, 



110 ; snail, 118 ; squid, 131 ; sea cucumber, 156. 

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



156. 

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



attached ; Nereis, 64 ; mussel, 91 ; clam, 105. 

 Rostrum : a projection of the carapace in crustaceans, 29. 



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



grasshopper, 15 ; snail, 118 ; squid, 131. 

 Scaphognathite : the elongated epipodite of the second maxilla in certain 



crustaceans, 34. 



