i 3 2 COMPARATIVE PHYSIOLOGY OF THE BRAIN* 



take hold strongly ; stimulation of the posterior stump 

 causes the suckers to let go and the arms to be with- 

 drawn. Thus the antagonistic activities of the arms 

 depend upon two different parts of the central nervous 

 system. " An animal whose supracesophageal mass 

 has been divided in the vicinity of the first central 

 ganglion behaves like an animal that is only able to 

 take hold of objects. It grasps every object firmly 

 and liberates itself again only with difficulty. It 

 usually retains its hold and sits with extended arms, 

 or crawls forward with the greatest difficulty. Such 

 an animal placed on the back of a torpedo seizes it 

 firmly with the arms, and no shocks of the electric 

 organs are of avail to rid the fish of its burdensome 

 rider. On the other hand, it is evident that the Ele- 

 done only participates in the ride involuntarily from 

 the fact that it becomes dark brown and throws ink. 

 If a normal Octopus by mistake grasps after a tor- 

 pedo, it never remains in so dangerous a neighbor- 

 hood more than a few seconds [I have observed 

 this in Octopus, never in Eledone]." It seems to me 

 that the conclusion to be drawn from these facts is, 

 that the anterior and posterior parts of the supra- 

 cesophageal ganglion are connected with antagonistic 

 muscle-groups. This relation is of interest in view of 

 galvanotropic experiments, which we shall discuss 

 later on. It is furthermore probable from v. Uex- 

 kiill's experiments that the act of eating depends upon 

 the integrity of the first central ganglion, while the 

 second and third central ganglia are necessary for all 



