254 



DESCRIPTIONS OF PREPARATIONS. 



52. Paramecium A^lrel^a and Amoeba Proteus. 



With Figure 13. 



Paramecium Aurelia, the Slipper Animalcule (Fig. 13, A. B. and i, 2, 

 3, 4), is commonly found in pond water and vegetable infusions. The 

 length of its body varies from T Jo to V of an inch. It is more or less 

 asymmetrical in shape, and one surface is slightly convex, the other flat. 

 As the latter is pierced by the pharynx it is generally termed ventral. 

 The exact outline varies somewhat with the state of contraction of the 

 animal. 



The surface of the body is covered by a very delicate cuticle (B : /.) 

 secreted by the underlying protoplasm and pierced by pores through which 

 pass the cilia. Paramecium is holotrichous, i. e. the cilia covering the body 

 are equal in size. There are larger adoral cilia leading to the pharynx, as 

 there are in some Holotricha. The cilia (A : B : .) are disposed in longi- 



Pig. 13. A. and B. Paramecium : from Ray Lankester, op. cit. infra, Fig. xxv. i and 2. 

 i, 2, 3, 4. Formation of vacuole : (after the same Fig. xxv)/ 

 C. Amoeba Proteus : from Leidy, op. cit. infra, PI. i. Fig. 4. 



tudinal lines on the surface of the body (A.) and extend into the pharynx 

 (B : /.), in which they create a current, up one side and down the other. 

 They are, therefore, not only organs of locomotion but also of alimentation. 

 They are structurally filamentous extensions of the cortical layer of the 

 protoplasm, and undergo alternate movements of flexion and erection, which 

 commencing at one pole of the organism, are propagated in successive waves 

 to the other pole. The protoplasm which makes up the' whole substance 

 of this unicellular animal is divisible into two parts, an external cortical 

 layer (B : C.) surrounding a central medulla (B : M.). These two parts are 

 sharply contrasted. The cortex is contractile, dense, hyaline, and of great 



