90 G. H. PAEKER 



8. If a Metridium is cut vertically in two except for a small 

 connecting bridge near the pedal edge of the column, the me- 

 chanical stimulation of the column of one part is followed by 

 oral-disc retractions in both parts. 



9. If a INIetridium is cut through vertically except for its oral 

 disc, the mechanical stimulation of the column of one part is 

 follow^ed by a contraction of the longitudinal mesenteric muscles 

 of both parts, thus demonstrating transverse nervous connec- 

 tions in the oral disc. 



10. If the column of a large Metridium with a pedal disc over 

 10 cm. in diameter is cut through in an oblong outline, 4 cm. by 

 2 cm. (fig. 3), a superficial piece of the column results that is 



Fig. 2 Oral view of a Metridium from which an edge of tissue has been cut 

 (Experiment 6); X, region of stimulation. 



attached to the rest of the animal only through its mesenteries. 

 Nevertheless when the middle of this piece (X) is stimulated me- 

 chanically or by discharging on it a small amount of hydro- 

 chloric acid in sea-water, a withdrawal of the whole oral disc 

 follows. This response ceases when all the organic connections 

 of the piece with the rest of the animal are severed by cutting 

 through the attached mesenteries, thus allowing the piece simply 

 to lie in place. The cessation of response under these circiun- 

 stances shows that the transmission must be nervous and not 

 due either to the mechanical effects of the contraction of the 

 piece itself on the rest of the animal, nor to an accidental over- 

 flow of acid. 



