AMCEBA. 3 



or more highly refractive than the rest of the 

 endosarc. During life it is easily seen in speci- 

 mens free from food. To stain it, place some 

 Amoebae on a cover-slip, and invert this over a 

 bottle of glacial acetic acid. Dry slightly over 

 a small flame, and stain with hematoxylin. 

 More than one nucleus may be present, but they 

 are all equivalent. 



Movements. 



The change of form already referred to is known as 

 amoeboid movement,' a form of that elongation and con- 

 traction seen best in muscle. Pseudopodia are protruded 

 com any point of the surface, and can be completely with- 

 drawn, and a slow crawling movement of the whole animal 

 can be effected by their means. Pseudopodia may also 

 surround algae and then be withdrawn, bringing the food 

 into the body. 



Draw a specimen of Amoeba several times at intervals of 

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

 )y means of at rows. Compare the drawings, and note the 

 differences of form even in sluggish specimens in which move- 

 ment was not obvious. 



Feed with indigo or carmine, or other finely divided pig- 

 ment, and note that food is taken in at almost 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 ectosarc of the original cell. 



E. Encystation. 



Amceba periodically and also under adverse conditions 

 assumes a spherical shape and secretes a cyst round itself. 

 These cysts may be either resting-cysts or reproductive cysts 

 From the former the Amoeba emerges unchanged. From 

 the latter it issues (in one marine species at least) as a cloud 

 of excessively minute flagellated spores which conjugate in 



