580 T. H. Morgan and N. M. Stevens. 



again no difference could be detected in the rate of regeneration 

 at the three levels or in comparison with the check series. These 

 results seem to indicate that the rate of development is not deter- 

 mined by the nearness of the new cut surface to the region where 

 a hydranth has developed, and thus supports the view that the 

 material that is made use of in the formation of a polyp comes 

 mainly from the polyp-forming region and not from the whole 

 stem (except perhaps to a slight extent from the broken down 

 ridges from the aboral end as will be spoken of below.) It is 

 true that pieces kept under artificial conditions regenerate after 

 a time less rapidly than fresh pieces, but this may be due to 

 general exhaustion of food substances thoughout the piece, so that 

 there is relatively less material from which to produce a new 

 polyp. 



Experiment 13. The more rapid development of the aboral 

 polyp when a ligature is tied around the stem has already been 

 noted by Driesch, Morgan and Loeb. In Tuhularia jiiarina the 

 aboral polyp so seldom develops in pieces left on the bottom of 

 a dish that this method and that of sticking the oral end into 

 sand or vaseline is the best way to obtain heteromorphic regen- 

 eration. Loeb found that it makes little if any difference in the 

 time of appearance of the hydranth, how far the ligature was 

 from the basal end. As this result has a direct bearing on our 

 problem we repeated the experiment a number of times and 

 under somewhat different conditions. In the first series some 

 pieces (cut very long) were tied August i, 10.00 a. m., near the 

 polyp, others near the middle of the stem, and others near the 

 basal end. Three days later one tied in the middle had an 

 aboral polyp; seven hours later one of the pieces tied near the 

 aboral end also had a polyp. During the four following days 

 no other aboral polyps developed. In another series (August i, 

 10.15 ^- "^O after three days, one piece tied near the polyp, one 

 tied in the middle, and one tied near the aboral end had polyps. 

 The next day another tied near the polyp had regenerated, and 

 the day following another tied near the polyp had an aboral 

 hydranth. No more developed during the next two days. 



In another series (August i, 5.00 p. m.) one piece tied near the 



