G. H. PARKER 233 



sensitive to mechanical contact but only moderately so to electrical 

 stimulation. It was, therefore, important to place the electrodes in 

 position without disturbing the animal and to stimulate with the 

 electric current only after all possibiHty of mechanical disturbance 

 had been passed. The response of the animal was recorded on the 

 drum of the kymograph by a dehcate heart lever which was attached 

 by a thread and hook to the lip of the sea anemone. As a matter of 

 good fortune the lip of Metridium is extremely insensitive and a 

 hook m.ay be passed through it and drawn up lightly without calling 



Fig. 2. Kymograph record in which the lowest Hne represents time in fiftieths 

 of a second, the middle line the moment of apphcation of the stimulus, and the 

 uppermost line the response of the sea anemone. The stimulus was appHed at 

 position 1 (Fig. 1). 



forth any particular response on the part of the animal. With this 

 attachment the sHghtest contraction of the longitudinal muscles of 

 the mesenteries was easily observed. 



Large specimens of Metridium were allowed to attach themselves 

 to sheets of glass about 15 cm. square. After they had firmly fixed 

 themselves, each one was subjected to the following procedure. 

 After the necessary connections between the animal and the kymo- 

 graph were made, an electric stimulus was appHed to the pedal edge 

 of the column and the normal reaction time, as indicated by the re- 

 traction of the oral disc, was determined (Fig. 2). The long tongue 



