204 



ROTIFERA 



CHAP. 



Brachionus, Hydatina, and Synchaeta, since the groove is replaced 

 by a zone of lappets, as above mentioned. In Proales the whole 

 face of the disc is strongly ciliated. The wreath is reduced 

 in the parasitic genera Drilophagus, Albertia, Balatro, and the 



Fig. 109. Callidina symbiotica. (After Zelinka.) A, Ventral view, with the disc half 

 expanded, proboscis extended ; B, lateral view, proboscis extended ; C, ventral 

 view of anterior segments with expanded disc ; D, lateral view of same (proboscis 

 retracted), a, Antenna ; bl, bladder (enlargement of rectum) ; c, ciliated cup of 

 the proboscis ; ci, cingulum ; cl, cloaca ; cp, group of pores, the openings of cement 

 glands ; di, disc ; g, gizzard ; gin, germarium (that of the opposite side seen at a 

 higher level) ; gr, ciliated groove ; k, kidney ; I, lip ; in, mouth ; pr, proboscis ; sp, 

 spurs of foot ; tr, large cilia of trochus, showing vertical movements ; vm, yolk- 

 gland. The body muscles are represented by shaded bands. 



Seisonaceae ; in Adineta and Taphrocampa it is only represented 

 by a general but scanty ciliation of the disc. 



The head is very frequently retractile, as a whole, by strong 

 muscles. In Bdelloida the disc proper is retracted when the 

 animal crawls, while the proboscis is exserted (Fig. 109). 

 Ciliated patches occurring outside the region of the disc point to 



