2^6 OTT. [Vol. VII. 



rounded by many smaller ones i /a to 1.5 /x in diameter (Fig. 

 II, O). In some cells the small globules are not present, and 

 the large globules are much larger than in cells where the small 

 ones are present (Fig. 12, O). 



When the living worm is studied, it can be seen that when 

 it takes food the anterior end of the pharynx is brought down 

 nearly to a level with the body wall, thus drawing the pharynx 

 out into a long narrow tube. The mouth is also seen to be 

 opened wide. At the same time the wall of the cone-shaped 

 depression is protruded and forms a circular ridge on the body 

 wall bordering a cup-shaped depression at the bottom of which 

 is the mouth opening. When the pharynx is in this position, 

 the worm moves about among the food particles floating in the 

 water. The rapid movement of the cilia, both of the depression 

 and of the pharynx, causes a current of water containing food 

 particles to flow into the mouth opening. This current of food 

 particles is kept moving in at the mouth for some time ; then 

 the worm quickly contracts the wall of the pharynx so that it 

 takes the form of a hollow sphere. The circular ridge on the 

 body wall surrounding the mouth opening disappears, having 

 been drawn in by the contraction of the pharynx. At the same 

 time the mouth is closed and the further contraction of the 

 pharynx forces the food through the valve into the intestine. 

 This valve is so arranged that its normal position allows food 

 to pass into the intestine while it does not allow it to pass out. 



As soon as the food is in the intestine, the worm seeks more 

 and takes it in the manner described above. While it is taking 

 this food, that which it has already taken remains in the intes- 

 tine, being held there by the valve. 



Occasionally the worm may be seen to contract the integu- 

 ment of the posterior part of the body and at the same time to 

 contract the walls of the intestine. At the same time the whole 

 pharynx is thrown forward and the mouth is brought wide open 

 to the surface of the body. When this is accomplished, a mass 

 of waste material and undigested food is extruded. After this 

 the worm immediately resumes its natural position. 



Thus it may be seen that the mouth is not only the place 

 where the food is taken in, but also the opening through which 

 the worm rids itself of refuse matter (Graff, '82, p. 97). 



When the worm takes food the mouth may be opened by the 



