On Asplanehna Ebhesbormi. By Dr. Hudson. 623 



as to be as broad as the base of the pharynx itself. Then the 

 contents of the stomach were thrust up through the pharynx so as 

 to come within reach of the curved jaws. These seized the yellow 

 mass, and slowly dragged it up right out of the pharynx, and jerked 

 it away through the mouth. It did not add to my respect for the 

 rotifer, that, not content with this uncomfortable method of getting 

 rid of indigestible material, it repeatedly swallowed the yellow ball, 

 to have it again dragged out by the teeth and again engulfed in 

 the pharynx. 



The Female. 



Nutritive System. — The structure of the female closely re- 

 sembles that of the other species of Asplanehna. The jaws 

 (fig. 15) are like those of A. Briglitwellii and A. Sieboldii ; and as 

 in the latter, two sets of muscles that work the jaws can be easily 

 seen in the living animal. First there are the muscles that are 

 attached to the free end of the fulcrum, and to the processes at the 

 base of either jaw. These clearly open the jaws. Next there is a 

 large muscle, which crosses the jaws transversely, and is attached 

 at either end to a Y-shaped process on each jaw. This evidently 

 shuts the jaws. The whole apparatus is imbedded in a stout horse- 

 shoe-shaped ring (figs. 12, 13, 14) that is much denser than any 

 part of the body except the jaws themselves : it dissolves however 

 under the action of caustic potash. The jaws lie on a sort of shelf 

 which floors the closed half of the horseshoe, and in front of them 

 is the rectangular opening of the mouth. The head consists 

 mainly of two low conical protuberances, whose bases are in the 

 ciliated rim of the trochal disk. They are confluent at the dorsal 

 surface, and on the ventral they unite together so as to form a 

 funnel leading to the mouth, which is pretty nearly in the centre 

 of the disk ; the funnel — the " proventricular canal " as Gosse has 

 well named it — sloping backwards and downwards from the ventral 

 surface towards the mouth. 



The ciliated rim dips down on either side of the ventral surface 

 so as to form a Y ; and just behind it, guarding the entrance to the 

 funnel, are two papillae armed with large vibrating setae. The 

 trochal disk is interrupted in no less than six places by notches, in 

 which are placed similar large vibrating setae. Two of these are 

 on the dorsal surface, two on the ventral, and one on each side. 



Below the horseshoe-shaped ring inclosing the jaws, and just 

 under the mouth, lies the pharynx. It is a very delicate membrane, 

 capable of great expansion, and seems to be kept in the shape of a 

 roughly cubical box by a kind of framework of four slender curved 

 rods which dip down from the head, and are united two and two on 

 each side by curved transverse pieces so as to make the base of the 

 crop rectangular. The whole apparatus resembles a waste-paper 



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