CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OP THE MUSEUM OP COMPARATIVE ZOOLOGY 

 AT HARVARD COLLEGE, NO. 232 



WOUND CLOSURE AND POLARITY IN THE TENTACLE 

 OF METRIDIUM MARGINATUM 



WAYLAND M. CHESTER 



EIGHT FIGURES 



The following study was begun by S. Stillman Berry and the 

 author at the Zoological Laboratory of Harvard University in 

 1909, and continued by the author at Woods Hole during the 

 summer of 19n. Mr. Berry should be particularly credited with 

 the initiation of the work on polarity, and I have made use of 

 his notes and compared his results with mine in the progress of 

 the study. I am indebted to Dr. Herbert W. Rand, under whose 

 direction the study was made, for many helpful suggestions. 

 Thanks are due Dr. F. B. Sumner, as Director of the Laboratory 

 of the Bureau of Fisheries at Woods Hole, for facilities for work 

 during the summer of 19n. 



The only previous study of the wound reactions of the tentacles 

 of actinians is that of Rand ('09). He described and analyzed the 

 activities involved in the closing of wounded tentacles and dis- 

 cussed the phenomena of polarity in the large southern forms, 

 Condylactis and Aiptasia, found at Bermuda. 



WOUND CLOSURE 



The present observations were made upon medium sized indi- 

 viduals of Metridium marginatum. When expanded, the column 

 carries a disk that is of larger diameter than the column and has 

 an outer zone, near its convoluted margin, of many rows of tenta- 

 cles, which are conical. Those of the inner row are somewhat 

 larger than the others. The animals used for experiment had 

 a column 25 to 35 mm. high and 25 to 30 mm. in diameter. The 

 tentacles of the inner row were 10 to 15 mm. in length with a 



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THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 13, NO. 3 



