CHAPTER VI 



EXPERIMENTS ON WORMS 



i. We shall consider separately in this chapter two 

 kinds of worms : first, those in which the ganglia are 



all crowded together in 

 the head end - - c. g. t 

 Planarians ; and second, 

 those with a series of 

 segmental ganglia - - c. 

 g., Annelids. 



Sea- and fresh - water 

 Planarians differ little 

 structurally, yet they 

 may show different re- 

 actions upon losing the 

 oral ganglion. 



Thysanozoon (Broc- 

 chii), Fig. 20, a marine 



FIG. 20. THYSANOZOON BROCCHII, A p lanari j s CQm . 



MARINE PLANARIAN. * 



mon in the Bay of Na- 



f, brain ; >, mouth ; , longitudinal nerve. J 



(Diagrammatic after Lang.) pleS. It is from I tO 3 



cm. long and nearly as broad. The oral end of 

 the body, which can be recognised by two tentacles 



