416 GENERAL HISTORY OF THE IXFUSORIA. 



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 r^zmi (g) articulated by a common base to 

 the extremity of a thin rod (fulcrum) (h) in such a way that they can open 

 and close by proper muscles. The fingers of each " uncus " rest upon the 

 corresponding ramus, to which they are attached by an elastic ligament. The 

 " mallei " are moved to and fro by distinct muscles ; and by the action of these 

 they approach and recede alternately, the " rami " opening and shutting 

 simultaneously, Avith a movement derived partly from the action of the 

 " mallei " and partly from their own proper muscles. 



Under all the variations in form and disposition of the parts presented in 

 Euchlanis, Anurcea, Synchceta, Diglena (XL. 24), PoJyartlira, Asplmichna, 

 Monocerca, &c., the same type prevails as in Brachionus (XL. 20-23) (which 

 is the genus Mr. Gosse uses as his standard of comparison). The modifica- 

 tions in those genera may in general " be considered as successive degenera- 

 tions of the ' mallei,' and augmentations of the incus. In another collection 

 of genera (the fixed or urceolate), the organs, although essentially the same 

 as in the former t}^e, are somewhat disguised by the excessive dilatation of 

 the * mallei,' and by the soldering of the unci and rami together into two 

 masses, each of which approaches in figure the quadrant of a sphere. The 

 ascribed ' stii^rup-shaped ' armature of the Philodincea arises from misappre- 

 hension ; for it has no essential diversity from the common type, their analogy 

 with the genera last mentioned being abundantly manifest, though they are 

 stiU fui'ther disguised by the obsolescence of the ' manubria.' In Floscularia 

 (XL. 25, 26) and Steplianoceros (XL. 27, 28) the most aberrant Rotatoria, 

 the * mastaoc ' is wanting ; and in the former genus the incus and manubria 

 are reduced to extreme evanescence, though the two -fingered unci show, 

 in their structure, relative position, and action, the true analogy of these 

 organs." 



As to their homology, he argues they have no true afiinity with the gastric 

 teeth of the Crustacea, though he states his conviction that the Rotifera belong 

 to the great Arthropodous division of animals. 



" The action of the homy jaws," Mr. Gosse remarks in his account of 

 Melicerta, '' is not exactly that of two flat-surface mullers, working on each 

 other in a grinding manner, but a complex motion impossible to be explained 

 by words." Since the nature of om- work has compelled us to limit ourselves 

 to a mere outline of Mr. Gosse's most elaborate and important researches on 

 the manducatory organs of the Botifera, we cannot too strongly recommend 

 the student to refer to that gentleman's essay in the Transactions of the Royal 

 Society, both for a more complete acquaintance with his A-iews and discoveries 

 relative to those particular organs, and for a host of valuable details on 

 other parts of the anatomy of this class of animals. 



Some Rotatoria, the so-called single-toothed species, have the faculty of 

 protruding their maxillae beyond the mouth, and of using them, in this curious 

 position, as prehensile organs. Thus the animal is enabled to seize upon 

 prey without awaiting its being casually engulfed within the vortex of its 

 ciliated head. Examples are found in Synchceta mordax, in Distemma 

 Forficula, and in Diglena (XL. 24). 



The maxillary bulb communicates immediately, or by the medium of a mem- 

 branous canal, with the stomach — the next division of the aHmentary tube. 

 This canal is very commonly termed the oesophagus ; but we prefer to call it 

 the pro ventricular canal, to avoid confusion and doubtful analogies. It com- 

 mences at the posterior inferior part of the bulb. 



