KEY TO CLASSES AND ORDERS OF ANIMALS 1$ 



2(1) Without lateral lines; alimentary canal incomplete or 

 absent in adults. 3 



3(4) Without a spiny proboscis at the anterior end. Adults 

 free living, long and very slender. (Pratt, 225; W. and 

 W., 537.) Class and order Gordiacea 



4(3) With a spiny proboscis at the anterior end. Without 

 a mouth and alimentary canal. Endoparasitic. 

 (Pratt, 228; W. and W., 545.) Class Acanthocephala 



Phylum TROCHELMINTHES 



I (4) External cilia present. 2 



2(3) Anterior ciliated disk present. (Pratt, 230; W. 

 and W., 587.) Class Rotifera, p. 15 



3(2) Only ventral surface ciliated; minute worms less than 

 five mm. long; body usually forked behind and fre- 

 quently covered with bristles. (Pratt, 243; W. and 

 W., 624.) Class and order Gastrotrlcha 



4(3) External cilia absent; marine. (Pratt, 244.) 



Class and order Kinorhyncha 



Class ROTIFERA 



(After Jennings in Ward and Whipple) 



1(2) Rotifers with two ovaries; creep like a leech but can 

 also swim by means of a crown of cilia. Body without 

 an outer shell or lorica; usually nearly cylindrical; 

 dorsal and ventral surfaces not greatly different; 

 body composed of rings which may telescope into one 

 another. (Pratt, 234; W. and W., 619.) 



Order Bdelloida 



2(1) Rotifers with one ovary; do not creep like a leech. 3 



3(4, 5) Mouth not near center of ciliary crown, which may be 

 ventral or terminal; free-swimming or creeping rotifers 

 but never creeping like a leech; one or two wreaths of 

 cilia but with the outer never shorter than the inner. 



