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MANUAL OF ZOOLOGY. 



tral surfaces. The "nucleus," which is truly an ovary, enlarges, 

 and a number of ovules are formed in its interior. In like 

 manner, the " nucleolus " of each, which is really a testis or sper- 

 marium, also enlarges, and develops in its interior a number 

 of fusiform or rod-like bodies, which are believed to be sperma- 

 tozoa. The nucleolus of each then passes into the body of 

 the other, the act of transference being effected through the 

 mouth. Contact of the two reproductive elements then takes 

 place, and a number of germs are produced, which, after their 

 liberation from the body of the parent, are developed into adult 

 Paramoecia. 



Vorticella (fig. n, <r) is a beautiful flower-like Infusorian 

 which is commonly found in fresh water, adhering to the 

 stems of aquatic plants. It consists of a bell-shaped body, or 

 " calyx," supported 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 presence in its interior of a spiral contractile fibre, 



Fig. 10. Morphology of Infusoria ; a Epistylis, a stalked Infusorian ; b 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 contractile vesicle and smaller food-vacuoles. 

 c Diagrammatic representation of Paramcecium, showing the funnel-shaped gullet, 

 the nucleus and nucleolus, food-vacuoles, and two contractile vesicles, d Aspidisca 

 lynceus ; e Peranema globulosa, a flagellate Infusorian. 



which is 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 commence- 

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

 situated the mouth, which conducts by its entrance or " vesti- 



