THE WHEEL ANIMALCULES (ROTATOR L\) 619 



138 (i) Two ovaries Subclass Digononta, 



In fresh water; only one group Order Bdelloida . . 139 



Free-living. Swimming with the corona or creeping hke a leech, or Ixjth. Bo^ly without 

 lorica, usually nearly cyHndrical, dorsal and ventral surfaces not being conspicuously differ- 

 entiated, and composed of rings which may be drawn one within the other in telescopic 

 fashion. A dorsal proboscis behind the corona; jaws ramate (Fig. 867). 



139 (146) Corona present i 



40 



140 (145) Corona of two nearly circular disks raised on short stalks, present- 

 ing the appearance of two wheels. 



Family Philodinid.vk . . 141 



141 (144) Eyes, two 142 



142 (143) Eyes in the dorsal proboscis Rotifer Schrank. 



Several species. 



Representative species (Fig. 958). . . Rotifer citriniis KhrcnbcrK. 

 (Fig. 960). . . . R. neptunius Ehrcnberg. 



143 (142) Eyes in the neck, directly over the brain, just above the jaws. 



Philodina Ehrenberg. 



Several species. 



Representative species (Fig. 959). . . Philodina roseola Ehrenberg. 

 (Fig. 867, A, page 577). . . P- brya-i Weber. 



144 (141) Eyes, none CaUidina Ehrenberg. 



The genus CalUdina when revised will be broken into several genera. Many species. 



Representative species (Fig. 961). • CaUidina angusticollis Murray. 



I4< (140) Corona a flat surface covered with cilia on the ventral side of the 



anterior end Family Vdinktidak. 



One genus only IJ/m/.i Hudson. 



Representative species (Fig. 957) Ulmeta vaga \hxy\,^. 



146 (139) No corona Family MICRODIMD.^K. 



The mouth has a group of cilia about it. 



One genus only ; ^. ' « ' „ "•''"""'{ ■""'">■• 



Representative species (Fig. <,6. and ^^^^^^Jj^Jii;^^,^,^, 



