6 THE PEOTOZOA 



2. The endosarc is the more fluid granular protoplasm 

 forming the central portion of the cell-body. 



a. The food-vacuoles are spherical spaces in the 



endosarc filled with water containing food- 

 particles. 



b. The circulation of the endosarc is rendered obvious 



by the food-vacuoles and the granules, which are 

 carried round in a definite direction. 



c. The nucleus is an elongated ovoid body near the 



centre of the cell-body. 



d. The paranucleus or ' nucleolus ' is a much smaller 



body applied to one side of the nucleus. The 

 term ' nucleolus ' is usually applied only to a 

 body placed within the nucleus of a cell ; the 

 name paranucleus is therefore to be preferred 

 for this extra-nuclear body. 



C. Reproduction. 



1. Fission is the most usual method, and is effected in the 



following manner. A transverse constriction appears 

 on the surface of the animal, and deepens till the 

 body is divided into two, each having a portion 

 of the original nucleus and paranucleus, and each 

 becoming a perfect Parameciura. 



2. Conjugation is not a mode of reproduction but is 



closely connected with it. Two Paramecia become 

 closely united by their ventral surfaces, and, after 

 swimming about together for. some time, separate 

 and become independent again. During and after 

 this union certain changes occur in the nuclei 

 and paranuclei of both individuals, resulting in 

 the so-called ' rejuvenescence of the nuclei,' and 

 followed by rapid and repeated fission of the two 

 Paramecia. 



