228 



INVERTEBRATE ZOOLOGY 



152 ; ambulacral system, 153 ; nerv- 

 ous system, 154 ; circulatory system, 

 154. 



Sessile ciliate, 188. 



Shrimp, freshwater : external parts, 

 48 ; appendages, 49. 



Simple ascidian, 135. 



Slipper animalcule, 184. 



Snail, see Land snail. 



Sow-bug : external parts, 46 ; append- 

 ages, 47. 



Spider, 24. 



Spongiaria, 181. 



Squid : external anatomy, 123 ; mantle 

 cavity, 125 ; excretory system, 127 ; 

 circulatory system, 129 ; respiratory 

 system, 129 ; digestive system, 130 ; 

 reproductive system, 132 ; nervous 

 system, 133 ; pen, 134. 



Starfish : external parts, 141 ; digest- 

 ive system, 145 ; reproductive sys- 

 tem, 145 ; ambulacral system, 146 ; 

 nervous system, 147 ; circulatory 

 system, 148. 



Strongylocentrotus, 149. 



Sycon sponge, 181. 



Taenia crassicollis, 80. 



Taenia saginata, 80. 



Taenia serrata, 80. 



Talorchestia, 48. 



Tapeworm : external form, 80 ; pro- 

 glottids, 81 ; encysted tapeworm, 

 83. 



Trachomedusa, 175. 



Tubularian hydromedusan : alterna- 

 tion of generations, 163 ; hydroid 

 stage, 163 ; medusoid stage, 167. 



Tunicata, 135. 



Turbellaria, 76. 



Unio, 89. 



Venus mercenaria, 103. 

 Vorticella : general form, 188 ; repro- 

 duction, 190 ; conjugation, 191. 

 Vorticellidae, 188. 



Wasp : external parts, 1 ; mouth-parts, 

 13. 



Zoothamnium, 188. 



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