THE AUTOTOMY OF THE HYDRANTH OF 



TUBULARIA. 



MAX MORSE. 



\Yhen colonies of Tubularia crocea are brought into the labo- 

 ratory, and placed in aquaria, they sooner or later lose their 

 hydranths. The hydranths become pinched off from the stems 

 and fall to the bottom of the aquaria where they disintegrate. 

 Later, new hydranths are regenerated in place of the old ones. 



Somewhat similar cases of the loss of the hydranth have been 

 reported by various workers on other species. All such in- 

 stances, however, involve an absorption of the hydranth, preceded 

 by a dissolution of the body through histolysis. Tubularia, 

 alone, is known to pinch off its hydranths completely from the 

 stems before extensive histolysis occurs or indeed, any what- 

 soever. 



Loeb 1 found in a species of Campanularia, an absorption of 

 the hydranth when the individual came into contact with the sides 

 of the dish or with any other solid object. Thacher 2 corrobo- 

 rated Loeb so far as an absorption occurred, but no evidence 

 of any effect of contact in producing the action could be deter- 

 mined. Loeb also reported absorption in two other genera, viz., 

 Margelis and Antennularia, where, however, the inciting cause 

 was believed by Loeb to be the changes the stems underwent 

 under the action of gravity. No one has studied this special 

 feature in these forms since Loeb. As will be spoken of later, 

 Tubularia does not show any such response. 



Thacher (/. c.) described absorption in two species of 

 Eudendriiun, E. raiiiosnin and E. tcnuc, and also in Pennaria 

 tiarclla. Pennaria caroliuii, an allied species, was studied by 



1 Loeb, J., " The Transformation and Regeneration of Organs," Amer. Jonrn. 

 Phys., Vol. 4, 1900. 



2 Thacher, H. F., " Absorption of the Hydranth in Hydroid Polyps," BIOL. 

 BULL., Vol. 5, p. 297. 



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