aquatic JLite 



51 



at any part of the surface, which is most 

 convenient. There is no stomach ; the 

 space occupied by the ingested food 

 serving- as an improvised one. There is 

 no anus ; the residual matter being pass- 

 ed out at the point most convenient. 

 Oxygen is absorbed by the surface of 

 the body, the contents oxidized, and 

 carbon dioxide given off. This shows 

 respiration in its most simple form. 

 Amoeba multiplies by division, that is. 



Amoeba 



VEHTAAL V1£V/ 



M«nt£ VACUOLE 



Paramecium 



it grows larger, becomes elongated and 

 the nucleus divides in half, a half going 

 to each end of the cell. Finally it be- 

 comes constricted in the centre and 

 breaks into two halves, each half be- 

 coming a complete new amoeba. This 

 process is not nearly as simple as it 

 seems, for there are numerous minute 

 changes going on among the finer par- 

 ticles of the protoplasm, and in the nu- 

 cleus. 



The next protozoan that we shall dis- 

 cuss belongs to the Infusoria, this is 

 Paramecium, the slipper animalcule, a 

 very good food for fry of egg-laying 

 fishes. Paramecium is slipper-shaped as 

 its name implies, and more pointed at 

 one end than at the other. Its whole 

 surface is covered with cilia or hair-like 

 projections, which wave actively back 

 and forth, and serve the purpose of pad- 

 dles, by means of which Paramecium 

 swims. At the more pointed end, 

 usually kept in the rear, is a group of 

 longer cilia, which seem to serve the 

 purpose of a rudder. Some times the 

 animal reverses ~its position and pro- 

 ceeds with the pointed end foremost, 

 but ordinarily for a short time only, 

 generally to back out of a tight place, 

 or when it comes in contact with some 

 obstruction, and desires a new start in 

 another direction. Along the flat sur- 

 face is a groove which at one end forms 

 a blind passageway, dipping into the 

 body. Both the groove and the tube, 

 which is the gullet, are lined with cilia. 

 By their vibrations these cilia collect 

 small one-celled plants, animals or other 

 particles of organic matter, which accu- 

 mulate at the inner end of the gullet. 

 From time to time this inner end is cut 

 off by constriction, and the collection of 

 food particles with some water is push- 

 ed into the soft protoplasm of the body. 

 It then becomes a food vacuole or im- 

 provised stomach. These food vacuoles 

 then slowly rotate around the body, and 

 when they reach a point opposite the 

 gullet, any undigested residue is ex- 

 pelled through a weak place in the wall, 

 there being no permanent anal opening. 

 In the outer portion, which corresponds 

 to the skin of the higher animals, are 

 numerous small sacs, each containing a 

 tiny thread. When the Paramecium is 

 irritated, it discharges these thread or 



