HARGITT. 



[VOL. I. 



narrow inlet. As this Medusa endures artificial conditions 

 with considerable ease for days and even weeks, it lends itself 

 readily to such experiments. Its size also, varying from 2 or 

 3 mm. to as many cm., is also a factor of convenience, though 

 a larger species would prove desirable in some operations. 

 Its activity during at least three months also facilitates ex- 

 tended experiments. 



II. Methods. 



In grafting the Hydroids, the stems were cut into fragments 

 varying from 5 to 10 mm. in length, and usually taken from 

 the younger and fresher portions of the stem. Successful 

 unions were made from older portions but in much smaller 

 proportions, and requiring much longer time. The hydranths 

 were excised, since the motion of the body and tentacles would 

 invariably disturb the contact of the specimens. Having pre- 

 pared suitable sections, they were brought 

 into contact in watch-glasses, or small petri 

 dishes, of perfectly fresh sea water, and re- 

 tained in position by small bits of lead shaved 

 freshly from thin sheets. Bits of platinum 

 wire would have been better, though it was 

 not available at the time, and little appreciable 

 difficulty was had with the lead. The water 

 was changed on the specimens daily. 



With the Medusae the task was a much 

 more difficult one, for while the power of 

 spontaneous movement had been largely elim- 

 inated by emarginating the bell and thus re- 

 moving the marginal nerve ring, and thus the 

 centers of spontaneity, the contractility had 

 not been destroyed, and for a time great diffi- 

 culty was found in retaining the parts in even 

 contact. And in this connection I desire to 

 correct a partial error in my previous paper 

 on " Regeneration," l where I had failed to recognize the 

 paralyzing effects of such emargination, a fact due to failure 



1 Zoological Bulletin, I, p. 29. 



FIG. j. 



