48 NORMAL HISTOLOGY. 



nucleoplasm. The C3^toplasm consists of two layers, the ectoplasm, 

 or dense, outer hyaline layer, and the endoplasm, or inner layer, 

 containing the microsomes. The nucleoplasm constitutes the nu- 

 cleus and contains masses of chromatin, which is very susceptible to 

 staining reagents. 



The animal has the power to throw out protrusions, or pseudo- 

 podia, from its body. A bulb is formed on the surface of the cyto- 

 plasm, and then all the protoplasm flows in this direction until, 

 often, the whole animal has passed into the pseudopodium. In the 

 meantime,, other pseudopodia are produced. The movement exhib- 

 ited by the leucocytes of the blood is similar to this and is called the 

 amoeboid movement. Food is obtained by flowing around it. There 

 nre two kinds of vacuoles, food vacuoles and water vacuoles. The 

 contractile vesicle serves the function of excretion. The Amoeba 

 reproduces by normal fission that is, the nucleus and protoplasm 

 divide into two masses, without undergoing any process of mitosis. 

 There are two stages of this animal, the active stage, just described, 

 and the encysted, or quiescent, state. When the animal is placed 

 under unfavorable conditions it contracts into a sphere, forms an 

 enclosing tough membrane, and in this condition may be wafted by 

 the air from place to place. Under favorable conditions the proto- 

 plasm breaks through the enclosing wall, and the animal again en- 

 ters the active stage. 



Habitat. The Amoeba may be found in ponds or brooks upon 

 submerged leaves and stems, or in the ooze which collects at the 

 bottom. To obtain material for laboratory use, collect some grass 

 and leaves from the side of a stream, also some submerged plants 

 and ooze from the bottom of a pond or stream, and place in glass 

 jars for five or six weeks. At the end of this period amoebas should 

 be obtained in numbers. 



Laboratory exercise No. 9. Amccbce. From the infusion, prepared 

 as directed, carefully pick out a submerged leaf, and apply some 

 of the ooze upon its surface to a slide. Cover and examine with 

 L. P. and H. P. Observe the ectoplasm, endbplasm, and nucleus. Make 

 out the vacuoles and contractile vesicles. Observe the formation of 

 pseudopodia. Make drawing's to illustrate protoplasm, nucleus, pseu- 

 dopodia, and encysted stage. 



