Introduction to Anijnal Morphology. 197 



lorica nor intestine. In Asplanchna there is an entire trochal 

 disc and toothed jaws. The male has two large and two 

 small pairs of limbs, but no muscles. Ascomorpha has no 

 water-vascular system, and rudimental, toothless jaws. Some 

 species, otherwise undistinguishable from Notommata, are 

 also aproctous (N. myrmeleo). 



Order 2. Hoiotrocha — proctuchous, disc entire, rounded, 

 including the families — i . Ptyguridae — only the post-abdomen 

 segmented ; disc circular, with one (Ptygura) or two crowns 

 ■of cilia (Diplotrocha). 2. QLcistidae — tail long; disc round 

 or elliptical ; eyes present in the embryo, persisting or 

 vanishing (CEcistes) ; body in cylindrical, yellow thecae, 

 fastened to the base, single (CEcistes), or in free colonies 

 (Conochilus). 



Order 3. Schizotrocha — proctuchous, trochal disc lobed, 

 notched, or divided, i. Megalotrochidae — deeply notched; 

 thecse none ; umbrella-shaped, free, and possessing eyes 

 when young, but the adults are sessile and blind. 2. Floscu- 

 larid^ — disc 2-4 lobed, or with 5-6 tentacles (Stephanoceros), 

 sometimes with two proboscides and a tubular lorica beset 

 with lenticular bodies (Melicerta). 3, Hydatinidae — un- 

 sheathed ; disc many-lobed. Pleurotrocha has one tooth and 

 no eyes. Hydatina has a short foot, no eyes, and several 

 teeth. Notommata has a nuchal eye. Hexarthra and Poly- 

 arthra have limb-like processes. Diglena has two frontal 

 eyes. Triophthalmus has three eyes. 4. Euchlanidae — like 

 the last, but loricated. Euchlanis has one eye-speck and a 

 short jointed foot. Salpina is pointed at each end, has one 

 eye and a dorsal groove. Metopidia has two eyes, and Lepa- 

 •della none. 



Order 4. Zygotrocha — two, simple, trochal discs, often 

 with a frontal lobe between them. Family i. Philodinidae — 

 naked, with a long divided tail ; jaws two, crescentic, with two 

 teeth on each ; often viviparous, with two frontal (Rotifer) 

 or nuchal eyes (Philodina, found in Alpine snows), or none 

 (Callidina). 2. Scaridinidae — foot with long joints, often 

 Avith long bristles ; not retractile ; skin soft (Scaridium), or 

 hard (Dinocharis). 3. Brachionidae — loricated, completely 

 enveloped behind (Anuraea), or with the foot passing through 



