FLAT WORMS 



41 



ectodermal cup. The cell within the cup enlarges and becomes the 

 lens. The lens is in this way derived from the nerve center. 



In Cercaiiaenum Bettendorf, 1897, shows six longitudinal 

 strands from the brain, with many branches to the pharynx and the 

 suckers. A complex nerve plexus of nerve fibers and nerve cells is 

 found over much of the body. Especially are bipolar sense cells 

 found in the pharynx. Similar bipolar sense cells are demonstrated 

 by Havet, 1900, by the Golgi method. 



Cestoda. The scolex contains the greatest concentration of 

 the nervous system although in Gnjocotyle there is fully as great a 



Fig. 12. The sketch at the top is from a section across a young; flatworm 

 showing the brain as a dark mass in the left side. The figure at the 

 left below is from a larval flatworm showing the position of twelve 

 simple eyes. The middle and lower left hand figures are from em- 

 bryonic stages of a nemertinian worm showing the developing nervous 

 system on the left and shown darker in the figures. Salensky. 



mass of central nervous system in the caudal end of the animal. 

 The suckers or other appendages of the scolex region are supplied 

 with special branches. In some forms there is a definite ring of 

 fibers. In all two larger and usually four smaller longitudinal 

 strands run the length of the animal. 



Blanchard, 1847, dissected the nervous system in Ligula where 

 he found a mass of nervous tissue in the scolex with strands run- 



