am(kb^;a. 



Sub-Class AMCEB^A. 



They may again be divided into the Lobosa nuda and the 

 Eeticulosa. The former inchide the AmcBbse (fig. 2). 



Amceba is a simple unprotected mass of protoplasm or sar- 

 code, which may be found in damp earth and in water. In 

 appearance it resembles a small speck of white, transparent, 

 structureless jelly. If this speck is observed under strong 

 magnifying power, it will be seen to move by throwing out 

 little finger-shaped processes, the pseudopodia (Psu). This 

 simple organism is apparently composed of two layers, a 

 granular layer inside and a clear transparent layer on the 

 outside : the former is known as the endosarc and the latter 

 as the ectosarc. These two layers must not be mistaken for 

 two distinct membranes, for they are continuous, only certain 

 granules collect towards the interior. ^Vhen the pseudo- 

 podia (Psu) are thrown out we shall see, if we watch care- 

 fully, that the granules flow up the centre of the process as it 

 elongates. Three other bodies are to be noticed in this minute 

 creature : first, a small dark oval spot, with a clear border and 

 permanent in shape, situated in the endosarc ; this is the iiurleuf: 

 ()i), and it will be found to stain dark-red with picro-carmine. 

 The nuclear substance or chromatin here is a single mass, but it 

 may be divided into portions, yet it can always be distinguished 

 from the body protoplasm or cytoplasm. There will also be 

 seen contracting and expanding a clear space in the ectoplasm ; 

 this is the so-called " pulsating vacuole " (i-v), of which there are 

 two in some forms of Protozoa (Pandnuriiim). The pulsating 

 vacuole is said to be an excretory organ, for uric acid and 

 water have been extracted from these minute cavities. These 

 vacuoles may bo looked upon as both respiratory and excretory. 

 Lastly, there are present a number of so-called " food vacuoles '' 

 (Pv), spaces surrounding the particles of food ingested by the 

 amceba. This proteus - animalcule is neither provided with 



