306 Account of Professor Ehrenlerg's 



by the names of Gymnogompbia, or those in which the teeth are 

 free, and Desmogomphia, in which they are fixed. Each of 

 these groups is again divisible into two. 



The two subdivisions of the Gyranogomphia are the Mono- 

 gomphia and Polygomphia. The first (Fig. 19, 20.) have only 

 one long tooth in each jaw, which they can push out a consi- 

 derable way, the teeth of the opposite sides then appearing like 

 a pair of nippers. The animals with this form of teeth are for 

 the most part very rapacious, and prey on other infusoria ; they 

 form, as it were, the ferae and carnivora of the tribe ; they are 

 more lively and quick in their movements than other rotatoria, 

 and, with one exception, they all possess eyes. The Polygom- 

 phia (Fig. 17, 18.) have more than one tooth in each jaw, some 

 have two, others from three to six. When there are several, 

 they, along with the maxilla, form the figure of a hand. The 

 animals of this division are less rapacious in their habits than 

 the former, and live chiefly on vegetable substances, or the 

 smaller infusoria which they attract by the currents which they 

 excite in the water ; they are never seen to attack the larger 

 Rotatoria, or to show other signs of a ravenous disposition. 



The group of Desmogomphia is less numerous than the fore- 

 going, but includes, as would appear, the most highly developed 

 Rotatoria. Its two subdivisions are the Zygogomphia and 

 Logogomphia. The animals of the first division (Fig. 21, 22.) 

 have in each of their stirrup-shaped jaws two teeth, alongside of 

 which the surface of the jaw is finely streaked in a parallel direc- 

 tion, as if it contained more teeth not perfectly formed. The 

 Logogomphia (Fig. 23, 24.) have always more than two teeth in 

 each jaw, which in other respects resemble those of the Zi/gogom- 

 phia, the collateral streaks on the jaw being well marked. In 

 respect of their mode of life, the animals of both these divisions 

 agree with the Polygomphia, living on vegetable matter. 



Lastly, a few of the Rotatoria are destitute of teeth. These 

 might be named Agomphia. 



Besides the proper jaws and teeth just described, some of the 

 Rotatoria are provided with an additional masticating apparatus, 

 which consists of indurated folds or ridges on the inner surface 

 of the pharynx, of a firmer consistence than the surrounding 

 substance, but yet not hard like the true teeth. 



