60 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



We see from this that quite complicated reactions 

 occur in these animals although they do not possess a 

 central nervous system like that in higher animals. 

 Were we to come across these same reactions in 

 higher animals we should be inclined a priori to as- 

 cribe them to the complicated structure of the central 

 nervous system. The experiments on Actinians will 

 perhaps prevent us from drawing such a conclusion 

 before we have forcible reasons for so doing. A high 

 degree of complication in the reactions of animals can 

 be reached where no central nervous system exists, or 

 where it serves only as a sensitive and quick proto- 

 plasmic conductor. The cause of complicated reac- 

 tions lies, therefore, in the irritabilities and structures 

 of the peripheral organs. 



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1. LOEB, J. Untersuchungen zur physiologischen Morphologic 

 der Thiere, I., 1891. Wurzburg, G. Hertz. 



2. LOEB, J. Zur Physiologic und Psychologic der Aktinien. 

 Pfliigers Archiv, Bd. lix., 1895. 



3. PARKER, G. H. The Reactions of Metridium to Food and 

 Other Substances. Bulletin of the Museum of Comparative Zoology 

 at Harvard College, vol. xxix., 1896. 



4. POLLOCK, W. H. On Indications of the Sense of Smell in 

 Actinia. Jour. Linnean Soc., London, vol. xvi., 1882. 



5. NAGEL, W. Experimented sinnesphysiologische Untersuch- 

 ungen an Coelenteraten. Pfluger's Archiv, Bd. Ivii., 1894. 



