158 ZOOLOGY 



u tape," absorbs fluid food, which soaks through its body 

 wall. As the segments at the older end of the animal 

 mature, they are set free and pass out of the alimentary 

 tract, to be picked up, perchance, in the food of an herb- 

 ivorous animal or else to perish. 



The economic importance of parasitic worms is very 

 great. Thus, although no great epidemics of the flukes 



have occurred in this coun- 

 try, a million sheep are 

 annually lost by this para- 

 site in Great Britain ; and 

 in 1879 and 1880 it was 

 estimated that three million 

 sheep died annually in 

 England alone of this 

 parasite. In Buenos Ayres, 

 during 1882, a million 

 sheep died of fluke disease. 

 By great care in prevent- 

 ing infection, especially 

 during damp seasons, we 

 may be able to prevent 



FIG. 148. Cerebratulus, a cream-colored any SUch disaster in this 

 nemertean. Head end at upper part of , . 



figure; mouth turned toward observer, C lW V" 



proboscis retracted. Instantaneous The group of Nemertini 



photograph of living worm by W.H.C. P. . ni . i , .- n , 



is allied to the flat worms. 



It includes chiefly marine animals, of somewhat flattened 

 form and great length, even as great as thirty metres. 

 They protrude a long, slender proboscis. These worms 

 are especially abundant in the sand of the seashore, 

 although land nemerteans occur. Cerebratulus (Fig. 148) 

 is a common form from the east coast. 



