294 



Philodina, Actinurus, &c. Here, however, the organs are proved to 

 have no essential diversity from the common type ; their analogy 

 with those last described being abundantly manifest, though they are 

 still further disguised by the obsolescence of the manubria. 



Floscularia and Stephanoceros, the most elegant, but the most 

 aberrant forms of Rotifera, close the series. The mastax, in these 

 genera, is wanting; and in the former genus the incus and the 

 manubria are reduced to extreme evanescence, thougli the two-fin- 

 gered unci show, in their structure, relative position and action, the 

 true analogy of these organs. 



Having thus shown that there is but one model of structure, how- 

 ever modified or disguised, in the manducatory organs of the Roti- 

 fera, the author proceeds to the question of their homology. He 

 argues on several grounds that they have no true affinity with the 

 gastric teeth of the Crustacea, though he states his conviction 

 that the Rotifera belong to the great Arthropodous division of 

 animals. 



It is with the Insecta that the author seeks to ally these minute 

 creatures ; and, by a course of argument founded on the peculiarities 

 of structure already detailed, he maintains the following identifica- 

 tions : that the mastax is a true mouth ; that the mallei are mandi- 

 bles ; the manubria possibly representing the cheeks, into which they 

 are articulated ; that the rami of the incus are maxilla ; and that the 

 fulcrum represents the cardines soldered together. 



While the author maintains the connexion of Rotifera with 

 Insecta, through these organs in their highest development, he 

 suggests their affinity with Poiyzoa, by the same organs at the 

 opposite extremity of the scale, since the oval muscular bulbs in 

 Bowerbankia, which approach and recede in their action on food, 

 seem to represent the quadriglobular masses of Limnias and Rotifer, 

 further degenerated. 



If this affinity be correctly indicated, the interesting fact is appa- 

 rent, that the Poiyzoa present the point where the two great parallel 

 divisions, Mollusca and Articulata, unite in their course towards 

 the true Polypi. 



Mr. Gosse's paper is illustrated by ninety-six figures of entire 

 Rotifera, or of the parts under review, all drawn from the life, and, 

 for the most part, with a power of 560 diameters. 



