G. H. PARKER. 



that would result in an appropriate geotropism. Such a form of 

 response is in essence that implied in the statocyst theory in which 

 the stimulus must be a deforming, not a general, pressure. But 

 whether in Ccntrechinus it is the spines or some other similarly 

 constructed organ that initiates the geotropic response remains to 



be ascertained. 



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