A Neiu Rotifer, Lacinidaria striolata. 25 



Lacinularia and fam. Melicertida. The finer teeth are at the 

 distal ends of the rami (Fig. 11, r.) and become gradually coarser 

 towards the fulcrum. In a definition of this type^ we find " unci 

 three-toothed; rami large, with many strife parallel to the teeth." 

 The appearances noticed both in dissolved out tropin and in 

 sections lead me to conclude that the striae here spoken of are 

 all teeth, which gradually diminish receding from the fulcrum, 

 or, that the whole of each uncus is a sheet stretching across from 

 the rami to the manubria in which the teeth are formed by 

 parallel thickenings. The fulcrum is imbedded in the mastax 

 at its ventral border (Fig. 9, ful.), so tliat the finer teeth are 

 near the oesophagus. The action of the whole mastax I take 

 to be as follows : — The food particles are admitted from the 

 pharynx through a valvular slit into the food cavity, which forms 

 in its ventral portion a flexible bag hanging in the mastax cavity, 

 the cilia on either side of the slit propel the matter onwards, 

 then the thick ridge of cilia on the roof comes into action 

 carrying it further and at the same time forces it down between 

 the teeth, while the cilia on the floor of the food cavity act from 

 below in a similar way. The unci as may be seen in the living 

 animal moving with a circular motion inwards and downwards 

 bringing the teeth together and separating them when the 

 motion is reversed. The food matter is thus received by the 

 coarse teeth and passed along to the finer until it reaches the 

 oesophagus. The use of the separating membrane appears 

 diflScult to understand, but I suggest that the mastax cavity 

 being filled with fluid exerts a pressure upon the separating 

 membrane and at the same time allows it to distend. This 

 pressure forcing up the sides of the separating membrane would, 

 together with the cilia of the roof, enable the animal to bring the 

 food matter between the teeth. The whole apparatus appears 

 adapted to dispose of the food matter which the trochal disc 

 automatically pours into the buccal cavity. In the first place 

 the pharyngeal end of the mastax may be closed, and the food 

 particles then issue from the posterior of the mouth as is seen 

 in the living animal \ then the joint action of the separating 

 membrane and the ciliated ridges keep the food under the 

 1 



1 The Rotifera. Hudson and Gosse, vol. i., p. 29. 



