248 ASEXUAL REPRODUCTION 



binary fission. In Spirogyra, the mitotic figure is clearly seen 

 when properly stained. As the cells of Spirogyra divide, they 



A yeast cell takes in food aad grows a bud which enlarges and produces other buds. This 



results in a chain or group of yeast cells. 



cling together end to end and form a long filament. Each cell 

 is an independent organism. Amitosis, (li^'isi()n without a spireme, 

 is very infrequent. There is doubt as to whether amitosis is ever 

 a method of reproduction in any normal and healthy cell. 



Many one-celled animals such as the Protozoa reproduce by 

 fission. In the amoeba, the nucleus divides mitotically, the 

 cytoplasm constricts between the two nuclei, and two new cells 

 are formed. The Paramecium, too, reproduces by a like method. 

 The micronucleus elongates, constricts, and divides. The 

 macronucleus resembles a degenerative nucleus in that it divides 

 amitotically. It frequently disintegrates and dies. Then the 

 micronucleus builds a new macronucleus. As the cytoplasm 

 constricts, a new mouth, groove, and gullet appear in one side of 

 the organism. A new vacuole appears at the end of each new^ 

 cell. The cytoplasm divides completely and the two new Para- 

 mecia swim awav from each other. 



Reproduction by budding. Another type of reproduction found 

 among simple organisms is budding. 



Problem. Study of budding in yeast cells. 



Break a small part of a compressed yeast cake into a dilute solution 

 of molasses. Stir and then let the mixture stand in a warm place over night. 

 Mount a drop of the material under the low power and then the high power of 

 the microscope. 



