HARGITT. 



held gently, by means of delicate forceps, in dishes of perfectly 

 fresh sea water. After the operation the specimens were im- 

 mediately transferred to clean sea water, which was afterward 

 changed at least daily and sometimes oftener. The specimens 

 were fed from time to time with bits of freshly killed shrimp or 

 small fish. The specimens usually seemed to thrive quite well 

 considering the artificial conditions under which they were placed 

 and the mutilation to which the operations had subjected them. 

 Occasionally, as will be noted later, whole sets under a given ex- 

 periment would seem to decline or go bad, a fact doubtless due 

 to accidental contamination of the water in which they were kept. 



I. EXPERIMENTS UPON THE REGENERATION OF THE MARGINAL 



ORGANS OF THE MEDUS/E. 



Hargitt '97, and Morgan 99, found that when the entire margin 

 was removed new tentacles regenerated though in their investi- 

 gations they remained rudimentary and bud-like. I repeated ex- 

 periments of a similar kind to see in how far my results would 

 confirm theirs. Five sets of experiments were tried. 



In all cases the cut edges contracted more or less. In the first 

 set the contraction continued till the edges had nearly met and 

 the bell was spherical and had only a very small opening into the 

 subumbrella. Five days after the operation small refractile bulbs 

 were found at the lower distal pole of the sphere, in several spec- 

 imens. The next day tentacles had begun to grow from these 

 bulbs. On the ninth day two to four tentacles were found on 

 those in which the bulbs had earlier formed. These tentacles 

 were of considerable length, had the rings of nematocysts and 

 the suctorial pads found in the mature tentacles (Fig. i). As 

 the opening was so small as to prevent the taking of food, the 

 specimens died before further developments could take place. 

 Particular care was taken to remove the entire margin with all 

 the tentacles and bulbs at the time of operation, so that these 

 regenerated tentacles were undoubtedly of new growth. 



In the second set the cut edges contracted, though not into a 

 sphere, and a large opening into the subumbrella was left. No 

 velum formed in any of the specimens. In two days several 

 bulbs had formed on some of the margins. In four days marginal 



