STBUOTUME OF ROTIFERS. 



Ill 



not over six, segments. A Kotifer may, in fact, be regarded 

 as an advanced trochos2}here or more properly ceplialula, and 

 comparable with the larvae or cephalulse of mollusks, Poly- 

 zoa, Brachiopoda and the Annelids. The alimentary canal 

 consists of a funnel-like cavity, the mouth, which may 

 be central, or situated on one side of the head ; it leads 

 to the madax or pharynx-like muscular sac, supporting 

 a comiDlicated 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 sali- 

 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 oesophagus, " a membranous 



fm 



LLi 



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 oesophagus 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 CiBca, while the intestine ends in a rectum 

 and cloaca, the latter opening at the base of 

 the tail. In Notomniata, the digestive canal 

 ends in a blind sac, and in such male Eotifers 

 as are known, there is no digestive cavity, the 

 canal being represented by a solid thread. 



There are no vascular or respiratoiy organs, but canijtl'^gg"™ 

 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. 



Fig. 132.— i?o- 

 tifevvulgai%s. c, 

 velum ; e, ma-^- 



