THE PEOTOZOA. 



II. PAKAMECIUM AURBLIA. 



This is a free-swimming freshwater protozoon found in 

 abundance amongst decaying vegetable matter. It differs 

 from Amoeba in its more definite shape ; in the more marked 

 differentiation of ectosarc and endosaro ; in the presence of 

 cilia and the absence of pseudopodia ; in its active locomotion 

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

 and of definite dorsal and ventral surfaces, and anterior and 

 posterior ends. 



N EP AV 



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

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



AV, anterior pulsating vacuole. EC, ectosarc : the lines running across 

 it indicate the tricliocysts. EN, endosaro. EP, paranucleus. EV, food- 

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

 groove. PV, posterior pulsating vacuole,in systole. TR, discharged trioho- 

 cyst threads. X, cilia. 



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. General appearance. 



The animal is an elongated somewhat flattened body 

 about y-J-u inch in length, rounded at its narrower anterior 

 end, and bluntly pointed at the broader posterior end. 



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. 



