Teeth of the Infusoria, 4S 



anew directed to the point, he prosecuted his researches, and has 

 since found six species of polygastric Infusoria, which clearly 

 exhibit a distinct pharynx and a masticating apparatus. 



Of these six species only one was previously known, the 

 Loxodes cuctiUulus; the five others had not previously been ob- 

 served or recorded; though the Professor observed them in very 

 great numbers in the spring of 1832. According to the situa- 

 tion of the mouth and vent, these Infusoria ought to be placed 

 in two different families, viz. in the Echelida and Trachelina ; 

 and if their external organization is considered, it will be found 

 they belong to three different genera. Their teeth may be more 

 easily observed than those of the Rotatoria, in which the animal 

 must be destroyed before the number is determined. The pha- 

 rynx is placed on the surface of the body, and often somewhat 

 projects from it. As we might expect, M. Ehrenberg regards 

 the dental apparatus so important, that, by its presence or ab- 

 sence, he determines species, and also uses it for the distinguish- 

 ing of genera. Thus, he has separated, to make distinct ge- 

 nera therewith, the I^xodes cucullulus, and all the other neigh- 

 bouring species which are provided with a masticating appara- 

 tus, although the rest of their organization would associate 

 them with the genera Loxodes, Holophrya^ and Biirsaria, in 

 which no such apparatus exists. The names he has given to 

 those Polygastria which have teeth, are Euodon cuculhdus 

 (Loxodes cucullulus), Nassula ornata, N'. elegans, N, aurea^ 

 Prorodon niveus^ and P. compressus. The three species united 

 in the genus Nassula are very interesting, in many points of 

 view, and were previously wholly unknown. 



As to their form and connections, the teeth of the polygastric 

 Infusoria differ from what is seen in the Rotatoria. The teeth 

 of the Kolpoda and the Bursaria present the form of a cylin- 

 der, or of a slender and long hollow cone. (See Plate I. fig. 2, 

 &c. in which a is the crown of the teeth). They are placed at the 

 entrance of the mouth ; they cover its interior surface, and are 

 disposed in series which closely approximate each other. Their 

 proportional length exceeds that of the rotatory animals. Their 

 anterior extremity is truncated, and their indentations are al- 

 ways more solid and distinct before than behind, where they are 

 more or less indistinct and mossy ; this is also remarked in the 



