GLOSSARY 205 



Subneural gland: a glandular body in ascidians, 128. 

 Subumbrella : the oral surface of a medusa, 153, 159. 

 Supporting layer: the non-cellular layer between the ectoderm and endo- 



derni in Hydrozoa; Hydra, 146; tubularian, 152; campanularian, 157. 

 Swimmeret: an abdominal appendage of a crustacean, a pleopod; crayfish 



or lobster, 26; crab, 37. 

 Symbiotic: the living together of two dissimilar organisms, each being 



dependent upon the other, 146. 

 Systemic heart: the median heart of the squid, 119. 



Tactile : relating to the sense of touch. 



Tarsus : the segmented foot of an insect ; wasp, 4 ; grasshopper, 10. 



Telson: the terminal segment of a crustacean, 25. 



Tentacle: an elongated tactile organ; Nereis, 56; Bugula, 80; snail, 104; 



Molgula, 125; Hydra, 145; tubularian, 150; campanularian, 156. 

 Tergite: the dorsal surface of an abdominal segment in insects, 3, 8. 

 Tergum : the dorsal surface of a thoracic segment in insects ; wasp, 3 ; 



grasshopper, 8. 



Terminal : towards or at the posterior or the distal end. 

 Test: the tunic of the ascidian, 125 : the rigid shell of the sea urchin. 

 Testis: the male sexual gland; grasshopper, 15; crayfish or lobster, 33; 



crab, 38; copepod, 49; Daphnia, 52; earthworm, 65; planarian, 71; 



tapeworm, 77; mussel, 91; clam, 100; squid, 122; starfish, 136; 



Hydra, 147. 

 Thorax: the body-division of arthropods following the head; wasp, 2; 



grasshopper, 7; caterpillar, 18; crayfish or lobster, 22; sow-bug, 40; 



amphipod, 42; Caprella, 44; larval decapods, 45; copepod, 47; 



Daphnia, 50. 

 Tibia : the segment of an insect leg between the femur and the tarsus ; 



wasp, 4 ; grasshopper, 10. 



Tiedemann's vesicles: minute diverticula of the ring canal of the star- 

 fish, 136. 

 Trachea : a respiratory tube in a tracheate arthropod ; grasshopper, 13 ; 



caterpillar, 19. 



Trichocyst: a cyst containing a defensive bristle in the ectosarc of Infu- 

 soria, 166. 

 Triclad : a division of planarian worms in which the intestine is composed 



of three branches, 70. 

 Trivium : the three rays of a starfish or sea urchin opposite to the bivium, 



133, 141. 



