STRUCTURE OF ROTIFERS. 135 
not over six, segments. A Rotifer may, in fact, be regarded 
as an advanced trochosphere or more properly cephalula, and 
comparable with the larve or cephalule of mollusks, Poly- 
zoa, Brachiopoda and the Annelids. ‘The alimentary canal 
consists of 4 funnel-like cavity, the mouth, which may 
be central, or situated on one side of the head; it leads 
to the mastaz or pharynx-like muscular sac, supporting 
a complicated set of chitinous teeth within (malleus 
and incus) which seize and masticate the food, which, 
through the rotary action of the velum, passes 
down the buccal channel or mouth-opening, and 
lodges within the mastax. The so-called suli- 
vary glands are two large, clear, vesicular 
glands, which are attached to the funnel and 
rest on the summit of the mastax. The latter 
opens into the cesophagus, ‘“‘a membranous 
tube, capable of great expansion and contraction, 
but varying much in length and diameter in 
different genera.” Gosse also states that a cur- 
rent of water appears to be almost constantly 
setting through the funnel and mastax, and 
thence through the esophagus into the stomach ; 
the latter is quite large, and provided with so- 
called ‘‘ pancreatic” glands, emptying into the’ 
anterior end. There are also hepatic follicles 
and ceca, while the intestine ends in a rectum 
and cloaca, the latter opening at the base of 
the tail. In Notommata, the digestive canal 
ends in a blind sac, and in such male Rotifers 
as are known, there is no digestive cavity, the rig. 92. —Zo- 
canal being represented by a solid thread. ol eae 
There are no vascular or respiratory organs, but {%j,% digestive 
a system of long, convoluted excretory tubes, 
one on each side of the body, which, as in the Trematodes 
and Cestodes, unite in a common, large contractile vesicle 
which opens into the end of the intestine. These tubes,: 
which are in places ciliated, correspond to the segmental or- 
gans of Annelids; they are open at the end, the cavity of 
the tubes thus communicating with the body-cavity. ‘ 
