52 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



-a. 



Cerianthus membranaceus, new tentacles could be pro- 

 duced by a lateral incision in the body of the animal. 

 But in some of these cases no mouth is formed. Fig. 



12 shows such an ani- 

 mal ; a is the normal, 

 b the new head. If the 

 incision was very small, 

 only single tentacles 

 were formed, without 

 the oral disc. These 

 new tentacles behave 

 toward food exactly 

 like the tentacles of the 

 old mouth. If we offer 

 FIG. 12. ACTINIAN (CERIANTHUS) WITH such a new head a 



A NORMAL HKAD (a) AND AN ARTI- . f 



FICIALLY PRODUCED HEAD (A). P iece of meat > the tent ' 



acles seize and press it 

 against the centre of 

 the oral disc, where the 

 mouth should be. After pressing in vain for some min- 

 utes the tentacles relax and the meat falls off. This 

 experiment could be repeated for months, in fact as 

 long as I observed the animal (2). In other cases the 

 second head was so near the old one that it was easy 

 to stimulate the tentacles of both simultaneously with 

 the same piece of meat. In this case a fight arose 

 between the two tentacle systems, each attempting to 

 draw the meat toward its own oral disc. Parker has 

 lately shown that even a single tentacle, after being 

 severed from the animal, grasps a piece of meat and 



Although the latter has no oral opening the ten- 

 tacles carry the meat to the place where the 

 mouth ought to be. 



