RECENT EXPERIMENTS ON REGENERATION. 



CHARLES W. HARGITT. 



DURING the summer of 1896 at the Marine Biological Labora- 

 tory the writer, while engaged upon the life history of some 

 of the Hyclrozoa, took occasion to repeat certain of the experi- 

 ments of Loeb, 1 Bickford, 2 and others upon regeneration and 

 heteromorphosis among hydroids, and to extend them to 

 several other forms. In the following paper it is proposed to 

 submit a synopsis of the several experiments made, with such 

 results as have sufficient definiteness to justify record. 



The work upon hydroids was restricted for the most part to 

 the genera Eudendrium., Pennaria, and Clava ; though some of 

 the experiments of the investigators named upon Tubularia, 

 Margelis, etc., were repeated, and with results quite as they 

 had reported. The work upon Eudendrium was quite as 

 demonstrative as either of the former, and that notwith- 

 standing the fact of its indisposition to take kindly to the 

 artificial conditions of the aquarium and its rather complex 

 character. Not only does Eudendrium readily regenerate 

 excised parts, such as stalk, hydranth, root, etc., but it exhibits 

 equally marked heteromorphism. Experiments upon the other 

 genera mentioned were of the same general nature and results. 

 Those upon Clava were somewhat limited, owing to the very 

 limited supply obtainable during the present summer. No 

 particular attention was devoted toward ascertaining immediate 

 causes by which to account for the phenomena. That external 

 conditions have much to do with certain aspects of it I have 

 no doubt but that they are the chief, or primary, conditions 

 seems at least an open question. Specimens placed under 

 identically similar conditions do not respond with equal 

 promptness nor with similar results. Many facts would seem 

 to indicate the operation of intrinsic factors. But of this it is 



1 Biological Lectures, 1893, p. 37. 

 - Joiii'ti. of Alorph., vol. ix, p. 417. 



