OF THE MANDUCATORY ORGANS IN THE CLASS ROTIFERA. 
423 
incorrect ; and the figures, with which they are illustrated, are but rude approxima- 
tions to verisimilitude. 
14. M. Dujardin sums up his observations on the same organs in the following 
words. After alluding to the Tardigrada, which he includes in his Systolides, the 
genus Enteroplea, which is said to be toothless, and the genera Floscularia and Lin- 
dia, which he describes (incorrectly) as lacking a ciliated mouth, he observes, — 
All the other Systolides, having jaws enclosed in a muscular pharyngeal bulb, 
which is moveable and protractile, at the bottom of a ciliated vestibule, may be 
distinguished according to the form of these jaws. Thus the Rotifers have their 
jaws in the form of a stirrup, opposed by the base, and bearing two or more small 
teeth, laid parallel, like arrows on a bow. The outer border, which is semicircular, 
furnishes a point of attachment for the muscles of the pharyngeal bulb ; and, drawn 
by them, it is strongly elevated and depressed, to produce, during manducation, the 
movement of the jaws. Their inner border is composed of two transverse bars, a 
little arched outwardly All the others . . . have jaws more resembling those of 
articulated animals, and composed of an assemblage of articulated pieces, which we 
may, up to a certain point, compare to the two pairs of mandibles and jaws, to the 
lips, to the tongue, and to the labial palpi of insects. In fact, in many of the Systo- 
lides we observe a central odd piece, on which are articulated two simple branches, 
which bear upon each other, or meet as by a hinge, in the midst of moveable and 
articulated pieces, supporting the jaws properly so called, and transmitting to them, 
thus, all the effort of the median muscular mass, to make them bite upon the prey, by 
furnishing to them et. point d'appui, when the lateral muscles draw back the external 
branches which carry the jaws 
15. The eminent French naturalist, in this description of the jaws, which appears 
to be drawn from the type found in such genera as Diglena and Albertia, has touched 
a key which might have unlocked the structure, not in a few genera only, but in the 
whole class of Rotifera. As it is, however, I cannot agree with Dr. Oskar Schmidt, 
that the arrangement and function of the teeth, and of the surrounding bulb, are so 
manifest as to need no further observation -I*. 
16. It may not be out of place to describe the manner in which the following 
observations were made. The desideratum was to obtain views of various aspects of 
the same animal ; particularly of the dorsal and ventral aspects, of the lateral, and 
of the vertical or frontal. But the minuteness of the objects, ranging from to 
-^th of an inch, precluded the possibility of affixing them to a needle, or other 
machinery, by which they could be made to revolve while in the field of vision ; and 
the more, since, being aquatic animals, they must be viewed immersed in water; a 
momentary removal causing the death of most species. The incessant activity of 
these little animals is also a great bar to accuracy of observation, if they be allowed . 
freedom ; and if we confine them by means of the compressorium, the form of their 
* Infusoires, p. 583, f Wiegmann’s Archiv, 1846, p. 69. 
