CHAPTER IV 

 EXPERIMENTS ON ACTINIANS 



i. The two preceding chapters have furnished 

 proof of the fact that the phenomena of purposeful 

 reflex action, of spontaneity, and of coordination are 

 determined, not by specific characters of the ganglion- 

 cells, but by general peculiarities common to all pro- 

 toplasm. These peculiarities are irritability and the 

 power of conducting stimuli, both of which will find 

 their explanation in the physics of colloidal sub- 

 stances. 



In this chapter we wish to put the foregoing con- 

 clusions to a test by showing that a group of animals 

 without any true central nervous system are able to 

 show reactions complex as those in higher animals. 

 Without such a parallel we should be more than 

 ready, in the case of higher animals, to attribute such 

 reactions to the specific structure of the ganglia or 

 the ganglion-cells. 



We cannot speak of a central nervous system in 

 Actinians in the same sense as in Ascidians. Under 

 the ectoderm there are elements which are interpreted 

 by some authors as ganglion-cells and nerve-fibres. 



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