292 



The reading of Mr. GOSSE'S paper, " On the Structure, Func- 

 tions, and Homology of the Manducatory Organs in the 

 Class Rotifera," was resumed and concluded. 



In this paper the author institutes an examination of the mandu- 

 catory organs in the class Rotifera, in order to show that the vari- 

 ous forms which they assume can all be reduced to a common type. 

 He further proposes to inquire what are the real homologues* of 

 these organs in the other classes of animals, and what light we can 

 gather, from their structure, on the question of the zoological rank 

 of the Rotifera. 



After an investigation of the bibliography of the class from Ehren- 

 berg to the present time, in which the vagueness and inexactitude 

 of our knowledge of these organs is shown, the author takes up, 

 one by one, the various phases which they assume throughout the 

 whole class ; commencing with Brachionus, in which they appear in 

 the highest state of development. Their form in this genus is there- 

 fore taken as the standard of comparison. 



The hemispherical bulb, which is so conspicuous in B. amphiceros, 

 lying across the breast, and containing organs which work vigorously 

 against each other, has long been recognized as an organ of mandu- 

 cation : it has been called the gizzard ; but the author proposes to 

 distinguish it by the term mastax. It is a trilobate muscular sac, 

 with walls varying much in thickness, receiving at the anterior ex- 

 tremity the buccal funnel, and on the dorsal side giving exit to the 

 oesophagus. 



Within this sac are placed two geniculate organs (the mallei), 

 and a third on which they work (the incus). Each malleus consists 

 of two parts (the manubrium and the uncus), united by a hinge-joint. 

 The manubrium is a piece of irregular form, consisting of carina of 

 solid matter, enclosing three areas, which are filled with a more 

 membranous substance. The uncus consists of several slender 

 pieces, more or less parallel, arranged like the teeth of a comb, or 

 like the fingers of a hand. 



The incus consists of two rami, which are articulated by a com- 

 mon base to the extremity of a thin rod (the fulcrum) , in such away 

 that they can open and close by proper muscles. The fingers of 



