PROTOZOA I INFUSORIA. 



61 



ported upon the extremity of a slender contractile stem or 

 ' pedicle.' The other extremity of the pedicle is fixed to some 

 foreign body, and its power of contraction is due to the pre- 

 sence in its interior of a spiral contractile fibre, which is 



Fig. 10. Morphology of Infusoria, a. EpistyUs, a stalked Infusorian. 6. A 

 single calyx of the same greatly magnified, showing the ciliated disc 

 which protrudes at will, and the ciliated internal cavity into which the 

 particles of food are received. In the substance of the body are the con- 

 tractile vesicle and smaller food-vacuoles. c. Diagrammatic representa- 

 tion of Paramoecium, showing the funnel-shaped gullet, the nucleus and 

 nucleolus, food-vacuoles, and two contractile vesicles, d. Aspidisca 

 lynceus. e. Peranema globulosa, a flagellate Infusorian. 



sometimes called the ' stem-muscle.' The edge of the bell, or 

 calyx, is surrounded by a projecting rim or border, called the 

 'peristome,' within which is a circular surface, the 'disc,' 

 forming the upper extremity of the so-called ' rotatory organ/ 

 The disc is surrounded by a fringe of vibratile cilia, forming a 

 spiral line which is prolonged into the commencement of the 

 digestive canal. Near the edge of the disc is situated the 

 mouth, which conducts by its entrance or ' vestibulum ' into 

 a fusiform canal or * pharynx,' which terminates abruptly in 

 the abdominal cavity. The particles of food are taken in at 

 the mouth, descend through the short alimentary canal, and 

 enter the abdominal cavity, where they are subjected to the 

 general rotation of the ' chyme-mass,' being finally excreted 

 by an anal aperture which is situated near the mouth. As in 

 Paramoecium, the body in Vurticella is composed of an outer 

 1 cuticle,' a central ' chyme-mass,' and an intermediate * cortical 

 layer,' which contains a contractile vesicle and a band-like 

 nucleus. 



Reproduction in VorUcella may take place by fission, or by 

 gemmation, or by a process of encystation and endogenous 



