LOCALISATION OP GEO-PERCEPTIVE LAYER 



49o 



E.cperiment 190. — A complete set of readings of the 

 geo-electric reictioii at liifferent layers of the organ was 

 taken, as the probe entereil the lower side by successive 

 steps of 2 mm. The following table gives the results 

 obtained with a specimen of Ni/mphci'a. 



TABLE XMII. — EI.KCTRIC KXPLORATION OF DIKKKRKNT I,AVKR« r.\ THE 

 LOWER S[nE f)K THE OR iAN (Ni/mphlfl). 



It is thus seen that just as in the upper so also in 

 the lower side, the electric variation undergoes at first an 

 increase which attains a maximum ; beyond this point the 

 electric change undergoes a rapid decline. The induced 

 electric change (»n the upper and lower sides are, however, 

 different, galvanometric negativify in one case and posi- 

 tivity in the other. 



The maximum galvanometric negativity of the upper 

 side was found to occur at the geo-perceptive layer. We 

 may next inquire about the anatomical characteristic of 

 the layer in the lower side of the organ which exhibits 

 the maximum galvanometric positivity. Microscopic section 

 of the specimen employed in the above experiment showed 

 the particular layer to be the starch crescent which lies 

 above the vascular bundle. Thus the same geotropic layer 

 which when placed above shows the maximum galvanometric 



