PARAMECIUM 3 



b. The pulsating vacuole is a space filled with a 



watery fluid. It is fairly constant in position, 

 and pulsates rhythmically. More than one may 

 be present. Time its pulsations. 



c. The nucleus is a spherical or ovoid body, denser 



than the rest of the endosarc ajid highly refrac- 

 tive. During life it is not easily seen, but it is 

 rendered obvious by killing the animal with 

 acetic acid (1 per cent.), or by staining with 

 magenta. More than one may be present. 



G. Movements. 



The constant but slow change of form already referred 

 to is known as ' amoeboid movement.' Pseudopodia are 

 protruded from any point of the surface, and can be com- 

 pletely withdrawn, and a slow crawling movement of the 

 whole animal can be effected by their means. Pseudopodia 

 may also surround particles of food and then be withdrawn, 

 bringing the food-particles into the body. 



Draiu a specimen of Amoeba several timss at intervals of 

 half a minute, indicating the direction of flow of the particles 

 by means of arrows. Compare the drauiings, and note the 

 differences of form even in sluggish specimens in which move- 

 ment was not obvious. 



Feed with indAgo or carmine, or other finel/y divided 

 pigment, and note that food is taken in at all parts of the 

 surface. 



D. Reproduction. 



Amoeba multiplies by fission ; that is, the whole mass 

 divides into two, each containing a portion of the nucleus, of 

 the endosarc, and of the eciosarc of the original cell. 



II. PAEAMECIUM AUEELIA. 



This is a free-swimming freshwater protozoon found 

 abundantly amongst decaying vegetable matter. It differs 

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

 differentiation of ectosarc and endosarc ; in the presence of 

 cilia and the absence of pseudopodia ; in its active locomotion 



