OF THE ROTATOEIA. 413 



animals, examined their ashes chemically, convinced himself they contained 

 much phosphate of lime, derived, as he supposed, from the maxillte. Mr. 

 Gosse likewise concludes that, from their great solidity and density, and 

 from the action of menstrua upon them, they are of calcareous nature. 



The construction of the jaws, and the number and position of the transverse 

 bars or ' teeth,' afforded Ehi^enberg characters of primaiy importance in the 

 construction of his system ; and he indicated three leading types, under which 

 all the Rotatoria could be classed, viz. : — " 1 , Affom^Jiia, toothless ; 2. Gym- 

 nogomphia, free-toothed (unconnected) ; 3. JDesmogomjphia, connected or 

 attached teeth. In Gymnogompliia the teeth are fi-ee in front, and, like 

 the fingers, united behind by a common band — the jaw ; in Desmogomj)hia 

 they are attached transversely across the jaw-piece, like an arrow lies across 

 the bow. In the former, again, the teeth in each jaw are single or several in 

 number ; in the latter, either two or manj'. Hence there are 5 groups : — 

 1. Agomphia — e.g. Iclithydium, Cluetonotus, Enteroplea) 2. Monogomphia 

 (one-toothed) — Pleurotrocha, Furcularia, Cycloglena, 3IonostyIa, Lepadella ; 

 3. Polygompliia (many-toothed) — Hydatina, several Notommatce, EucJdanis, 

 Steplianoceros, Bracliionus, (S:c. ; 4. Zygogomphia (twin-toothed) — CaUklinaj 

 Eotifer, Actinurus, Philodina, Monolahis, and Pterodina ; 5. Lochogomphia 

 (teeth set in rows) — Ptygura, Megalotrocha, Melicerta.^' 



This classification of the Eotatoria, however, Ehi^enberg confessed to be 

 imperfect, as wanting repeated researches to fix on the truly generic and 

 specific resemblances and difierences of the dental apparatus. In fact, 

 although the conditions may be constant in the same species, yet thet are so 

 minute, that they frequently can be made out very imperfectly and with un- 

 certainty ; and, besides this, the variations in the positions of the animal 

 when mo\Tiig its body appear so materially to alter the form of the mechanism 

 in question, that careful students often differ respecting it in the case of the 

 self-same animal. To illustrate these remarks, we may appeal to the descrip- 

 tion of MeUcerta ringeiis, as separately and independently detailed by Prof. 

 WiUiamson and by Mr. Gosse. The latter represents three or four transverse 

 bars or teeth to each lateral jaw (XXXYII. 23), the former above a dozen 

 (XXXYII. 26) ; the one detects a trilobed bulb, the other speaks of a single 

 conglobate organ, but which, from his figures, might be called bilobed. Addi- 

 tional illustrations of such doubt and uncertainty are to be found on compar- 

 ing the descriptions of the maxillary organs recounted by any two observers. 

 Ehrenberg's representations are now set aside by aU, improvements in the 

 microscope, and repeated examinations, having demonstrated their erroneous- 

 ness. The whole tribe of Agomphia or toothless Rotatoria must be set 

 aside ; for it seems a weU-established rule, that no female of the class is de- 

 ficient of dental organs, and the genera Iclithydium and Chrdonotus cannot, 

 as before shown, be retained in the class. Enteroplea, again, is in all proba- 

 bility a male animal, and Cyphonantes wants, according to Ehrenberg's plates, 

 the characteristic organization of Rotatoria in aU its details. But it would 

 be useless to continue an analysis of the other types established by the Berlin 

 Professor, the existence of any one of which, having the particulars of struc- 

 ture assigned to it, is not to be demonstrated. What is worse, we must con- 

 fess to the absence of any one detailed account of the dental apparatus which 

 can be received with implicit confidence in its accuracy ; so greatly have the 

 leading writers on the Rotatoria differed among themselves in describing the 

 mechanism in question. 



Dujardin distinguished the following parts in the maxillary apparatus : — 

 the ^'fulcrum'' or support, a single central piece with two articulated branches ; 

 the ■* scapus " or lateral branch ending in an articulated point, " acies," and 



