INFUSORIAL ANIMALCULES. 69 



member is a foot-like noii- articulated process, situated at 

 the ventral surface of the posterior part of the body. This 

 member is usually called the tail ; but being situated ante- 

 rior to the discharging orifice, is not properly such. It 

 has usually the faculty of being able to slide one part 

 within another, and presents to the observer the . same 

 effect as the moving of the sliding tubes of an opera-glass, 

 or telescope. The extremity is often formed in such a 

 manner that the creature can cause itself to adhere to any 

 substance, by forming an exhausted cavity within the 

 disc-like extremity, as is the case with the leech and some 

 parasitical acari found on beetles. Sometimes the termi- 

 nation of this false foot has two or more toe-like pro- 

 cesses. By the construction of this member, the creature 

 is enabled to attach itself, while the anterior part is 

 moving about in search of provender, and likewise to 

 employ it as an instrument of progression, by alternately 

 contracting and elongating it, and fixing itself by it and 

 the mouth. Muscles for moving the body, and also the 

 rotatory organs, are mostly visible ; these are known by 

 their thickening during contraction, and dilating when 

 elongated. 



Section XXX. — Nutritive System, 



The alimentary canal is mostly simple in all the Rota- 

 torial Infusoria. It is sometimes expanded near the 

 middle, in which case it may be said to have a true 

 stomach, the constricted commencement being an 

 oesophagus, and the long narrow termination a rectum. 



The manducatory, or chewing apparatus, situated at the 



