72. Body trumpet-shaped 



Stentor Oken 

 Body bag'Or purse-shaped 

 Bursaria Miiller 



73. With a narrow, neck-Hke or tail-Hke extension at one end of the body 74. 

 Not so 78. 



74. Posterior narrowed into a tail-hke region 



Uroleptus Ehrenberg 

 Anterior narrowed into a neck-Hke region 75. 



75. Neck short 76. 

 Neck long 77. 



76. Neck extensile 



Trachelophyllum Claparede and Lachmann 

 Neck not extensile 



Amphileptus Ehrenberg 



77. Body flat, ribbon-like 



Dileptus Dujardin 

 Body long-ovate, not flattened 

 Lacrymaria Ehrenberg 



78. Body, when extended, long and slender, worm-like 



Spirostomum Ehrenberg 

 Body not worm-like, not usually capable of great extension 79. 



79. With cilia on the ventral side; no cilia on the dorsal surface, but some- 



times with a few bristles dorsally; usually swimming or moving with 



one surface uppermost 80. 



With cilia all over the body; usually swimming with a revolving or 



spiral motion 83. 



80. With oblique rows of ventral cilia; on Hydra 



Kerona Ehrenberg 

 Ventral cilia scattered or in lengthwise rows; usually free-swimming 81. 



81. Anterior end asymmetrical 



Chilodonella. Strand 

 (Chilodon Ehrenberg) 

 Anterior end almost evenly rounded 82. 



82. With many cilia in lengthwise rows on the ventral surface 



Urostyla Ehrenberg 

 With scattered ventral cilia 



Oxytncha Ehrenberg 



83. Mouth almost or quite at the front end of the body 84. 

 Mouth set about one-fourth or more of the way back 85. 



84. Front end oblique, bearing the mouth 



Spathidium Dujardin 

 Animal evenly rounded on both ends 

 Prorodon Ehrenberg 



85. With a long groove leading to the mouth 86. 

 Not so 89. 



45 



