322 



ZOOLOGY 



SECT. 



ORDER 3. PLOIMA. 



Rotifera in which locomotion is performed by the ciliated disc 

 only. The tail is usually forked and more or less retractile. 



Sub-order a. Illoricata. 



Ploima in which the trunk is not covered by a lorica. 

 Including Hydatina, Polyarthm, Asplanchna, etc. 



Sub-order b. Loricata. 



Ploirna in which a lorica is present. 

 Including Brachionus, Euchlanis, etc. 



ce 



ORDER 4. SCIRTOPODA. 



Rotifera provided with setose appendages moved by striped 

 muscles : slapping movements are performed by the aid of these, 

 as well as swimming movements by the trochal disc. The tail is 



either absent or is repre- 

 sented by a pair of ciliated 

 processes. 



Including Pedalion and 

 Hexarthra. 

 -br 



ORDER 5. 

 TROCHOSPH^RID A . 



Globular Rotifera having 

 the trochal disc represented 

 by an equatorial circlet of 

 cilia ; tail absent. 



Including Trochosphcsra 

 only. 



ORDER 6. SEISONIDA. 



Marine parasitic Rotifers 

 (Fig. 273), with the trochal 

 disc reduced, the body long, 

 narrow, and ringed, with a 

 long slender neck-region, 

 and an elongated foot pro- 



, 273. Paraseison asplanchnus, female, -in . 



x 230. a. genital aperture ; br. ganglion ; /. Vlded at its extremity With 

 foot-glands; m. mouth ; ma. mastax ; oe. rrso- ii-f/vno-t-nrl A'IV 



pliagus ; ov. ovary ; st. stomach. (After Plate.) a P e 5C - 



FIG 



