2IO 



ROTIFERA 



ventral inlet from the pharynx, and a postero-dorsal outlet 

 through which the food passes into the stomach either directly 

 or through a slender gullet (Fig. 106, oe). In the ventral wall 

 of the gizzard of most Ploima is a median piece, the fulcrum, 

 from which run forwards and upwards two pieces, the rami, 

 which are hinged on the fulcrum. The Y-shaped structure 

 formed of these three pieces is called the incus (anvil). At 

 either side of the gizzard and at a higher level is a paired piece, 

 the malleus, so called from its resemblance to a hammer, of which 

 the manubrium (handle) looks backwards, and is embedded in 



FIG. 111. Diagram of trophi. (After Hudson.) A, Malleate ; B, submalleate ; C, 

 virgate ; D, forcipate ; E, malleoramate (Melicerta) ; F, incudate (Asplanchim) ; O, 

 uucinate (Stephanoceros) ; H, ramate (Rotifer), f, Fulcrum ; i, iucus ; wa, manu- 

 brium (malleus m O) ; r, ramus , un, uncus. 



the side walls of the niastax, while the toothed claw or uncus 

 looks forwards and inwards, and is hinged at its inner side with 

 the tip of the ramus. As the unci and rami are usually strongly 

 toothed, this gizzard forms a very efficient apparatus for chewing. 

 In some cases, when the pharynx is short and dilatable, the 

 points of the unci and rami may be protruded for biting, for 

 clinging to the host (in the parasitic genera Albertia and Drilo- 

 phagus), or for the prehension of food (Eattulidae, etc.). 



The type we have just described is termed the " malleate " 

 type (Fig. Ill, A). If all the trophi are slender and scarcely 

 toothed, we have the "virgate" type (C), which is frequently 



