346 ' A. J. Goldfarb 



The greatest regeneration occurred in i, then came 2 and 3, 

 which regenerated about the same number and less than i ; there 

 was a decided drop in 4 and 5 which regenerated least. There 

 was a notable exception in one of the dishes of series 5 in which 

 a surprisingly large number of polyps were produced. Direct 

 sunlight stimulates sterns to increased regeneration of polyps, even 

 though the temperature of the water in which they are contained 

 rises as high as 28° C. There is, furthermore, an undoubted posi- 

 tively phototropic bending of some of the new polyp-bearing 

 branches. 



EFFECTS OF TEMPERATURE'^ 



Experiment 24. In the previous experiments bacterial increase 

 was guarded against, particularly in the higher temperatures, 

 and hydranths prospered in a temperature as high as 28° C. 

 Without this precaution such high temperatures would be fatal 

 to the stems. At what higher temperature polyps would be regen- 

 erated was not determined. Up to a certain point the greater 

 the warmth the greater the regeneration. 



When stems were placed in a refrigerator in which the tempera- 

 ture varied from 10° to 16° C. there was no mistaking the inhibi- 

 tory effects of the cold. A large number of stems never regener- 

 ated at all, and the total number produced was exceedingly small. 



EFFECTS OF REPEATED REMOVAL OF POLYPS FROM THE SAME 

 LATERAL BRANCHES" 



Experiment 25. As soon as polyps were distinctly differentiated 

 at the cut ends, they were again amputated. This daily removal 

 of poylps was carried on for a period of 31 days, and daily records 

 made of the number and position of the polyps removed. During 

 this time there were regenerated : 



1 At 15 cut ends, including oral and basal, 59 different polyps; 



2 At 1 1 cut ends, including oral and basal, 28 different polyps; 



3 At 15 cut ends, including oral and basal, 64 different polyps, 

 making a total of 41 cut ends regenerating 151 new polyps or 368 

 per cent in 31 days. 



^^Peebles '98, on The Effects of Temperature on Reg. of Hydra, Zobl. Bull. 

 ^-Hargitt, G. T., '03, Reg. in Hydromedusa;, Archiv f. Ent. '03. 



