GLOSSARY 203 



Pulvillus : an adhesive pad between the claws on the foot of a grass- 

 hopper, 10. 



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

 going its metamorphosis. 



Racemose vesicles: minute diverticula of the ring canal in starfishes, 136. 

 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, 153, 159. 

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



cephalopods; snail, 110; squid, 122. 

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



131, 140. 



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

 hopper, 14; crab, 38; snail, 110. 



Rectal glands: glandular structures in the rectum of certain insects, 13. 

 Rectum : the posterior division of the digestive tract ; grasshopper, 13 ; 



caterpillar, 19 ; crayfish or lobster, 33 ; Bugula, 80 ; mussel, 90 ; clam, 



100 ; snail, 108 ; squid, 122. 

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



attached ; Nereis, 58 ; mussel, 85 ; clam, 95. 

 Rostrum : a projection of the carapace in crustaceans, 23. 



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



grasshopper, 13 ; snail, 108 ; squid, 121. 

 Scaphognathite : the elongated epipodite of the second maxilla in certain 



crustaceans, 28. 

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



in insects. 



Scolex: the anterior end of a tapeworm, 74. 

 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 ; Nereis, 57 ; 



earthworm, 63 ; mussel, 86 ; clam, 96. 

 Sessile : fixed to one place, without locomotory powers of an animal ; 



Bugula, 79; Molgula, 125; tubularian, 149; campanularian, 155; 



Grantia, 161 ; Vorticella, 168: not on a stalk or stem of an organ, 



40, 42, 153, 158. 



