THE PEOTOZOA 



by means of the cilia ; and in the possession of a definite 

 mouth, and of definite dorsal and ventral surfaces, and ante- 

 rior and posterior ends. 



Put a drop of water containing Paramecia on a slide ; 

 spread a very little cotton wool over it, to limit the move- 

 ments of the animals ; cover, and examine with low and high 

 powers. 



A. Oeueral appearance. 



The animal is an elongated, somewhat flattened body 

 about y^ inch in length, rounded at its narrower anterior 

 end, and bluntly pointed at the broader posterior end. 



N EjP 



Fig. 9. — Paramecium aurelia, seen from above and slightly from 

 the right side ; x 300. (c. h. h.) 



A.V, anterior pulsatujg vacuole. EC, eotosarc : tlie lines running across 

 it indicate the tricliocysts. EW, endosarc. EP, pai-anucleus. PV, food- 

 vacuole. M, mouth. MIT, ' myophan ' striation. M", nucleus. OG-, oral 

 groove. PV, posterior pulsating vacuole, in systole. TE, discharged tricho- 

 cyst threads. X, cilia. ^ 



It swims actively by means of cilia distributed over its 

 entire surface. Near the middle of the ventral or oral surface 

 is an oblique groove leading to the mouth. 



B. Structure. 



The two layers, eotosarc and endosarc, are much more 



sharply defined than in Amoeba. 



1, The eotosarc is the comparatively firm outer layer, the 



elasticity of which preserves the general form of the 



body. Its deeper part is marked by longitudinal 



or oblique ' myophan ' striations, which vary in dis- 



