146 THE ROTATORIA. '^ 130. 



dilatation. This dilatation is continuous into an intestine which opens exter- 

 nally by an anus. 



The mouth is always between the rotatory organs, so that it receives 

 what is drawn in by their vortical action, — the animal swallowing or re- 

 jecting the particles at will.*^^ 



The pharyngeal masticatory apparatus is round, and composed of two 

 jaws having one or several teeth, which are brought together laterally by 

 the action of special muscles. '''* 



Usually these jaws are formed of two knee-shaped divisions [Processus 

 anterior and posterior). The j)Osterior division gives insertion to the masti- 

 catory muscles, but the anterior terminates with a tooth,'"' or as a multi- 

 dentate apophysis.'^* With some which have this last arrangement,''"' the 

 two jaws are formed of three horny arches, and noted for their stirrup-like 

 form. Two of these arches {Aracs superior and iiiferior)^ form the arched 

 portion of the stirrup, pointing inwards, while its base is formed by the 

 third arch [Arcus externus), pointing outwards. The masticatory muscles 

 are inserted upon the inferior arch, and move against each other — the 

 transversely-arranged teeth passing over the other two. 



With the multidentate Mouotrocha, and Zygotrocha, the pharynx rests 

 always in the same locality ; but with the unidentate Polytrocha, it can 

 move up and down, and even be protruded through the mouth. In this 

 last case, the teeth serve as pincers for the seizure of food. The intestine 

 usually traverses the cavity of the body in a straight line, rarely loop- 

 ing,'*^' and is lined throughout with ciliated epithelium. 



From the stomachal dilatation to a point near the anus, its walls are 

 "very thick. The walls of the stomach and intestine are formed of large 

 cells with a colorless nucleus, and which, as they contain a brownish or 

 greenish granular substance, are of an hepatic nature. 



With most species, two caeca, rarely more, with thick walls and lined 

 with ciliated epithelium, open on the right and left of the beginning of the 

 stomach. Their walls are also composed of large cells, which, as they 

 differ widely from the hepatic ones by their colorless contents, may perhaps 

 serve the function of salivary glands or pancreas. ''^^ 



The terra llectum has been given to a short and terminal portion of the 

 intestine, which has thin walls, capable of being widely distended by feeces. 

 Its orifice is excretory not only of the fajces, but also of the contents of 

 the genital organs and of the aquiferous system — and may therefore be 

 regarded as a cloacal as well as an anal opening. It is nearly always at 

 the base of the caudal extremity. 



1 The teutaculifonn, rotatory organs of Stephana- size tliroughout, except the rectum which is dilated. 



ceros, are also used for the seizure of food ; see But it is coiled, especially with those which are 



Khrenberg, Alih-indl. d. Kerl. Akad. 1832, Taf. enclosed in a carapace, as with Tubicolaria, and 



XI. fig. 1, e., iilso, nie Jiifusionsthicrchen, Taf. Mclicerta, since here the anus is far in front. 

 XLV. fig. II. 5. " These two pancreatic caeca are nearly always 



'■>■ i'or the structure of the teeth, see Ehrenbers:, present, being wanting only with some species of 



Abhand. d. Bed. Akad. 1831, p. 'ifi, Taf. 111. IV. Jchthydiiim. With Notommata ckwuhita, aiu! 



3 Plcurotrocha, Furcii/aria, and many species Diglena larustris. tlirre are, besides these caecL 



of Notommata, and Diglena. which are long, attached to the stomach many 



■♦ Hydatina, Euc/ilanis, Salpina, Anuraea, smaller sacs, which are colorless and perhaps of 



Bracliionug, and many sjiecies of Notommata, the same nature. 

 and Diglena. With Megalotrocha albo-flavicans, there are 



& P/iilodina, Lacinnlaria, Melicerta, and also two like caecal appendages entering the base 



Conockilu.<!. of the stomach, and wiiich are indeijendent of the 



6 Viith Euchlaiiis, and Brachioniis, the stom- short pancreatic on' s of the same locality; see 



ach is separated from the intestine by a constric- Ehrenberg, Abhaudl. d. Berl. Akad. 1831, Taf. 



Uon, aud with Philodina, the intestine is of e(jual III. and, l»ie Infuaionsthiercheu, Tuf. L. LIV. 



