Vol. XX. December, 1910. No. i 



BIOLOGICAL BULLETIN 



FURTHER EXPERIMENTS ON ADVENTITIOUS 



REPRODUCTION AND POLARITY IN 



HARENACTIS. 



C. M. CHILD. 

 WITH ELEVEN FIGURES. 



INTRODUCTORY. 



In a paper which appeared in IQO9 1 I described the adventitious 

 formation of new axes in the Calif ornian actinian, Harenactis 

 attenuate,. These new axes have thus far been observed only 

 under certain conditions, viz., in isolated pieces prepared in such 

 manner that the oral cut surface of the body wall unites with 

 the aboral about the whole circumference. In my earlier paper 

 such pieces were designated as "rings." 



During the past summer I again enjoyed the privileges of the 

 laboratory at La Jolla and take this opportunity of expressing 

 my thanks to the director, Professor Ritter, and to the trustees 

 of the San Diego Marine Biological Association. During my 

 stay at La Jolla I obtained results with "rings" from Harenactis 

 which supplement my earlier work and extend and confirm my 

 conclusions. These results form the subject of the present paper. 



As described in my earlier paper, the rings are produced by 

 isolating rather short, cylindrical pieces from the body of Harenac- 

 tis by means of transverse cuts (Fig. i), and then removing more 

 or less completely from these pieces the mesenteries and mesen- 

 terial muscles. The region of the body proximal to the esophagus 

 is the most suitable for such operations, since here the mesenteries 

 are well developed, bear large retractor muscles and extend into 

 the enteron with free borders instead of being attached to the 



J Ch Id, 'ogb, "Factors of Form Regulation in Harenactis attenuata, III., Regu- 

 lation in 'Rings,' " Journ. Exf>. Zoo/., VII 2, 1909. 



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