FLAT WORMS 



39 



longitudinal cords. A short distance from the brain the anterior 

 nerves are united into a curved ganglion and from this a number of 

 branches run to the anterior end of the body. On the mid-dorsal 

 line a small median nerve in Epidella runs towards the head and 

 towards the sucker, but was not found farther than this. 



In the main nerve strands and ganglionic areas bipolar cells 

 are of frequent occurrence and generally one branch from each 

 might be traced close to the surface of the body while the other 

 fiber passes into the brain. In a few cases the fibers pass to the 

 opposite side of the ganglion or brain before they terminate. Cells 

 with three branches in Epidella were found with one process to the 



Fig. 10. Trematode worms. A, B, D, Monogenetic forms. C, E, F. G, Dige- 

 netic. A. Nervou.s system Tristoniiim. B. Head end of Epidella, 

 Health. D. Eyes of Epidellu, Health. C. Amphintomum, Loos. E. 

 Sensory cells of trematode, Havest. F. Nervous system of Cerca- 

 rioenum, Bettendorf. G. Nerve plexus Corcoriaeniim, Bettendorf. 



brain, another to the substance of the sucker of the same side, and 

 the other crosses over to the Sucker of the opposite side. 



In Epidella, the large mass of nerve fibers and the more numer- 

 ous longitudinal bands on the ventral side are explained by the 

 fact that this side rests against the host. 



There are four eyes in Epidella. In other forms they seem not 



