Flatworms arid Roundworms 371 



Coordination and Sensory Equipment. — A bilobed, diffuse mass of 

 nerve cells known as the cerebral ganglion (brain) is located beneath the 

 pair of sensitive eye spots just posterior to the pair of sensitive auricles. 

 Numerous nerves connect the brain with the sense organs in the anterior 

 part of Planaria. Two ventral nerve cords extend backward, laterally 



Cerebrals 

 (jatKjIion 



LonqitudinaL 

 nerve cord 



Testis 



VasQ 



efferentia 



Lateral 



nerve 



Auricle 



_^_-Eyc 

 _\ Ovary 



Vos J 



deferens 



Mouth \_^^ 



Sem'mcl 



vesicle 



Sern'inal 



receptacle 



— .Yolk cjlar)ds 



Lateral nerve 



Intestine 



_J)/Vcrticula 



lumen of 



pharynx 



N_. Intestine 



_Oviduct 



Pharyngeal 



chamber 



Penis 



Qenitalpore 



Fig. 179. — Dugesia (Planaria) (reproductive system). The male organs are 

 shown on one side only. (From Potter: Textbook of Zoology, The G. V. Mosby 

 Co.) 



