process of binary fusion in Paramecium
Paramecium reproduces asexually by transverse binary fission under good conditions of food. In this division a single individual divides into two daughter individuals by a horizontal or transverse division. First, the Parameciurlt stops feeding and its oral groove disappears. The micronucleus divides into two by mitosis division. The resulting two daughter micronuclei move towards opposite ends of the cell. The macronucleus divides amitotically by simply becoming.elongated and constricted in the middle. Meanwhile, a transverse groove forms around the middle of’the body, and continues to grow deeper. Before separation each halfdevelops new parts like .cytopharynx, contractile vacuoles etc. to become’complete P a ramec i um. The constriction deepens dividing the old individual into two daughter individuals. The anterior one is called proter and the posterior one is opisthe. Thus, two daughter paramecia, almost equal-sized and each with a complete set of cell organelles, are obtained from a single parent. These grow to full size and start leading free existence. The process is completed within 30 to 120 minutes depending upon the condition of temperature and food. It may occur 2 to 3 times a day. The binary fission cannot go on indefinitely. After sever4l generations, the rate of fission gradually declines.