ROTIFEBA 



235 



2 or 4 spurs a little way up; a dorsal proboscis behind the corona; 

 ovaries 2: 2 families. 



Family PHILODINIDAE. 



Corona composed of 2 circular and separated retractile lobes, making 

 2 distinct wheels; proboscis and tentacle present: 4 genera. 



Key to the genera of Philodinidae here described : 



Oi Two eyes present. 



6i Ej^es on the proboscis 1. Rotifer 



62 Eyes on neck, directly over the brain and the jaws 2. Philodina 



ttj Eyes absent 3. Callidina 



1. Rotifer Schrank. Body long and slender and 

 very retractile: among plants and dirt: 9 species. 



R. vulgaris Schrank (Fig. 374). Body whitish and 

 opaque, gradually tapering to the foot, which makes 

 up half the animal ; spurs not twice as long as width of 

 body; length .5 mm.: common; also in salt water. 



R. tardigradus Ehrenberg. Body dark brown in 

 color, long and slender; spurs 3 times as long as the 

 width of body where attached ; length .8 mm. : common. 



2. Philodina Ehrenberg. Body rather thick, fusi- 



form; 2 red eyes behind the pro- 

 boscis; often in infusions: 6 species. 



P. aculeata Ehr. Dorsal surface of body beset with 

 strong spines; length .5 mm.: common. 



P. roseola Ehr. (Fig. 375). Body rather slender 

 and often rose-colored; foot not distinctly set off; 

 length .5 mm. : common. 



3. Callidina Ehrenberg. Body elongate, without 

 eyes, the jaws often with fine transverse ridges : many 

 species. 



C. elegans Ehr. Each jaw with 10 ridges, cuticula 



Fig. 374 



Rotifer vulgaris 



(Sussw. F. Deut.). 



A, the animal. 



B, head end. 



1, proboscis 



2, eyes 

 3, tentacle. 



Fig. 375 

 Philodina roseola 



(from 

 Sussw. F. Deut.). 



smooth ; length .35 mm. : common in infusion. 



Order 3. PLOIMA. 



Non-tubicolous rotifers, which swim and do not creep like a leech, 

 but may creep with the toes or may leap ; some are parasitic : 2 suborders. 



Key to the suborders of Ploima: 



Oi Without shell (lorica) 1. Illoeicata 



Cj With lorica 2. Loricata 



Suborder 1. ILLORICATA. 



Ploimate rotifers with a flexible cuticula and no shell (lorica) : 6 

 families. 



