ROTIFERA. 



123 



51, e, e) communicating with that enlarged portion of the 

 digestive canal (c) which may be looked upon as the proper 

 stomach. 



(161.) We must now revert to the consideration of the 

 dental apparatus contained in the gizzard, represented in situ in 

 (fig- 49, /), and exhi- Fig. 50. 



bited on a still larger 

 scale in (fig- 50, 2). 

 This curious masticat- 

 ing instrument consists 

 of three distinct pieces 

 or teeth, which are 

 made to work upon 

 each other by the con- 

 tractions of the gizzard, 

 so as to tear in pieces or 

 bruise all matters made 

 to pass through the 

 cavity containing them. 

 The central piece (Jig. 

 50, 2, 1) may be com- 

 pared to an anvil pre- 

 senting upon its upper 

 surface two flattened 

 facets ; and upon these 

 the other two teeth, that might without much stretch of 

 fancy be compared to two hammers, act. Each of the superior teeth 

 (fig. 50, a, a) may be described as consisting of two portions 

 united at an angle : the larger portion, or handle as it might be 

 called, serves for the attachment of muscles ; whilst the other 

 part is free in the cavity of the gizzard, and works upon the facets 

 of the anvil, the edge being apparently divided into teeth resem- 

 bling those of a comb, and evidently adapted to bruise or tear 

 substances submitted to their action. Such is the transparency 

 of the whole animal, that the effect of these remarkable masti- 

 cating organs upon the animalcules used as food is distinctly 

 visible under a good microscope, and if the Rotifer be compressed 

 between two pieces of glass, so as to break down the soft textures 

 of its body, the teeth may from their hardness be procured in a 

 detached state for minute examination. The whole apparatus 

 described above evidently resembles very closely the kind of 





