DR. MOXON ON THE ANATOMY OF ROTATORIA. 457 
necessary to place them so that their pedunculated feelers point in opposite directions ; 
any ganglion in the oral side of the neck of Melicerta will be on the side opposite that 
wherein the ganglion of Philodina is seated, whilst the cloace will open on corresponding 
sides. 
The structure and disposition of the alimentary canal in Rotatoria have already been the 
subject of much attentive observation, and little can remain for further discovery, though 
a comparative examination of the gizzard-teeth of all the genera would produce interesting 
results. The approaches to the gizzard are more elaborate in the stationary genera, and 
reach their highest complexity in Floscularia (fig. 1). In this creature the part of the 
alimentary canal above the gizzard is divided by a highly irritable cilium-clothed 
sphincter of irregular outline (fig. 1c) into two portions, one of which is the great bell- 
shaped orifice with its five-lobed seta-bearing rim, and the other a cavity whose walls are 
powerfully contractile. To this second or pharyngeal cavity immediately succeeds the 
true gizzard, containing the crushing-machine (fig. 1 e). The cavity of the gizzard in 
Floscularia is much more capacious than in any other Rotifer ; and this becomes especially 
striking through the smallness of the dental apparatus, which is composed of small two- 
toothed nippers at the bottom of the cavity and towards the dorsal side. The prey, instead 
of being drifted down the throat by a cilium-current, is swallowed by a true act of deglu- 
tition; food is brought into the oral cup by that vortex which is created by the quick cilia 
that cover the faucial sphincter ; after a few revolutions within the mouth it is presently 
passed into the pharyngeal cavity, the faucial sphincter closing behind and preventing 
return, whilst a sudden and almost convulsive contraction of the walls of the pharyngeal 
cavity forces the morsel into the gizzard or crop, through the narrow fissure-like opening 
which leads into it. It should here be remarked that with the edges of this opening à 
thin-walled, flattened, cilium-lined tube (fig. ld) is continuous, and depends freely in 
the cavity of the gizzard ; the movement of the cilia within this freely suspended tube 
causes it to wave about in the gizzard, in the same way as the esophagus of Metopidia is 
kept in constant agitation by its lining cilia. When the prey reaches the crop it is still 
alive, and often remains so for many minutes, making meanwhile violent efforts to 
escape, which would be likely to prove successful if it were not for the flattened tubular 
Valve; this, whilst allowing, and aiding with its cilia, the entrance of prey forced in by 
the pharynx, is admirably suited to prevent any from finding or forcing its way back 
again: as it is only in Floscularia that prey is detained in the crop, 0 only in Floscularia 
18 the tube valve required or developed. d 
This tube valve has often been seen by describers, but its nature has ‘been: € y 
mistaken; it has been viewed as a “slit-like opening fringed with vibratile cilia "*, as 
“many plates or filaments t, as two delicate membranes}, and as a stream of rod 
trickling into the gizzard, To inspect it a three-parts-grown specimen should be chosen, 
Whose anatomy will not be obscured with those refracting grains W. 
adults, If the tube be watched by daylight with a good microscope, 
ich are developed in 
its true nature will 
* Dobie, Ann. Nat. Hist. 1849, No. 22, vol. iv. 
T Dujardin, Hist. Nat. des Zoophytes, P- 611. To 
t Huxley, Trans. of Micr. Soc., new series, vol. i., 1853. 
i dam eT ee ee EEN a T 
