EXPERIMENTS ON WORMS 



Si 



pieces containing brain and eyes, the reaction be- 

 gan about one minute after exposure to light ; in the 

 pieces without brain, after about five minutes. In this 

 experiment, only diffused daylight was employed as a 

 stimulus. In a round dish with vertical sides, the 

 Planarians do not collect, like strictly heliotropic ani- 

 mals, on the window- or room-side of the dish, but on 

 the right and left sides. Decapitated Planarians be- 

 have in the same way. All these reactions occur the 

 day after the operation. Fresh 

 material should always be used for 

 these experiments. 



After what has been said, it is 

 hardly necessary to mention that 

 pieces of Planaria torva from which 



the brain has been removed right 

 themselves as well as normal animals. 

 According to some authors, the 

 starfish represents a colony of as 

 many individuals as it has arms. 

 We have seen that these react har- 

 moniously as long as the nervOUS FIG. 24. TWO-HEADED 

 connection is uninterrupted. In 

 Actinians that have been made two- 

 headed artificially, this harmony no 

 longer exists ; for instance, in taking food both heads 

 struggle for the same piece of meat. At my suggest- 

 ion, Dr. van Duyne tried to produce multi-headed 

 Planarians artificially. He succeeded in making 

 them with as many as six heads. Fig. 24 shows a 



PLANARIAN PRODUCED 

 ARTIFICIALLY. (After 

 van Duyne.) 



