NERVOUS TRANSMISSION 



91 



died (Fig. 21), a stimulus applied to the pedal edge of 

 the column will call forth a contraction of the oral disc 

 even more readily than when it is applied to the portion 

 of the column that is on, the oral side of the circular in- 

 cision. Hence it must be admitted that there are trans- 

 mission tracts that lead from the 

 ectoderm of the pedal edge of the 

 column directly through to the 

 longitudinal muscles of the mes- 

 enteries irrespective of such con- 

 nections as may exist in the 

 oesophagus. 



The same conclusion can be 

 drawn from what is seen in prep- 

 arations from which the whole 

 oral disc has been cut off. On 

 stimulating the pedal edge of 

 such a preparation the portions 

 of the longitudinal muscles of the 

 mesenteries still remaining in the animal contract vigor- 

 ously, showing that there is not only a direct connection 

 between the ectoderm of the pedal edge of the column and 

 the longitudinal muscles of the mesenteries, but that the 

 oral disc, believed by the Hertwigs to contain a central- 

 ized portion of the nervous system of the actinian, is in no 

 way essential to the reaction noted. The belief that the 

 oral disc does not contain an essential nervous center 

 has already been vigorously set forth by Jordan (1908). 



If the column of a large sea-anemone with a pedal 

 disc 10 centimeters or more in diameter is cut through in 

 an oblong outline, 4 centimeters by 2 centimeters, a super- 

 ficial piece of the column results that is attached to the 

 rest of the animal only through its mesenteries (Fig. 22). 



FIG. 21. Metndium with its 

 column wall completely girdled by 

 a cut that passes at all points en- 

 tirely through the wall. Stimulus 

 applied at z. 



