NERVOUS TRANSMISSION 



95 



to the cut is never followed by a retraction of the disc 

 even though the two faces of the cut are in contact. 



If a sea-anemone is cut through vertically except for 

 its oral disc (Fig. 27), the mechanical stimulation of the 

 column of one part is followed by a contraction of the 

 longitudinal mesenteric muscles of both parts, thus dem- 



Fio. 27. Metridium cut through verti- 

 cally except for its oral disc. Stimulus ap- 

 plied at x. 



FIG. 28. Metridium cut through verti- 

 cally except for its aboral disc. Stimulus 

 applied at x. 



onstrating transverse nervous connections in the oral disc. 



If the sea-anemone is cut through vertically as de- 

 scribed in the preceding paragraph, except that the con- 

 necting portion is the pedal disc instead of the oral disc 

 (Fig. 28), the stimulation of one part is followed by the 

 retraction of the halves of the oral disc in both parts. 

 Thus the pedal disc as well as the oral disc can serve the 

 animal for transverse nervous connections. 



Finally, if a sea-anemone is cut vertically in two, ex- 

 cept for a small connecting bridge near the pedal edge of 

 the column (Fig. 29), the mechanical stimulation of the 

 column of one part is followed by a retraction of the 

 halves of the oral disc in both parts. 



These various tests and experiments show that the 



