470 WAYLAND M. CHESTER 



Inverse grafts of two tentacle fragments, base to base, or tip to 

 tip, show no reversion of ciliary action. The reactions to touch, 

 and the closure of cut ends in such grafts are the same as in similar 

 fragments which have not been grafted. 



In regard to the character of the mechanism involved in the 

 polarity of muscle action — the proximal muscular response to 

 touch and the temporary closure of a distal wound by a muscular 

 sphincter — my experiments add little to what is already known for 

 other sea anemones. The results do not show with any definite- 

 ness to what extent the muscles involved in the movement or 

 closure of the tentacle are dependent on nerve mechanism. This 

 point is fully discussed by Rand with reference to the results of 

 the study of other sea anemones. My results upon Metridium 

 are similar to his. We might infer that the Metridium tentacle 

 contains very short nerve fibers in which the impulse runs only 

 toward the base of the tentacle, and that there are separate sets 

 of nerve cells for the endodermal circular and the ectodermal 

 longitudinal muscles. But it must be remembered as an argument 

 against the existence of such a simple mechanism that Rand 

 found evidence of a reversal of polarity in distal pieces of Con- 

 dylactis tentacles, where proximal cut ends exhibited temporarily 

 a more or less distinct nipple. If the muscle fibers, and particu- 

 larly the circular ones, act without nerve control, it is still not clear 

 why there should be one result on one side and another on the 

 opposite side of the same plane of cutting. 



LITERATURE CITED 



Rand, H. W. 1909 Wound reparation and polarity in tentacles of Actinians. 

 Jour. Exp. ZooL, vol. 7, pp. 189-238, 2 plates. 



Parker, G. H. 1896 The reactions of Metridium to food and other substances. 

 Bull. Mus. Comp. Zool. Harvard College, vol. 29, no. 2, pp. 107-119. 



