6 THE PROTOZOA. 



then be seen radiating from them. They also 

 open to the exterior at the same moment. 



e. The oral groove runs obliquely backwards along the 



ventral surface from near the anterior end to the 

 mouth, which is placed a little behind the middle 

 of the length of the animal. Its cilia are fused 

 to form an undulating membrane, and drive water 

 and food particles into the mouth. 



f. The mouth is an oval aperture in the ectosarc at 



the hinder end of the oral groove, through which 

 the food passes into the endosarc. 



g. The anus is an aperture between the mouth and 



the hinder end of the body. It is visible only at 

 the moment of extrusion of fsecal matter. 



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 mega-nucleus is an elongated ovoid body near 



the centre of the cell-body. 



d. The micro-nucleus is a much smaller body applied 



to one side of the mega-nucleus, and of an entirely 

 different character. In some species there are 

 two micro-nuclei. 



C. Reproduction. 



Fission is the only known 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 mega-nucleus and micro 

 nucleus, and each becoming^, perfect Paramecium. 



