Factors 111 Regeneration 343 



the scattered stems. When the crowded stems were removed 

 from the groove and separated from one another, there was a mark- 

 edly increased regeneration. 



Experiment 21. Dr. Louis Murbach kindly permitted me to 

 use an ingenious apparatus devised by him, by means of which a 

 stream of air bubbles was introduced at the bottom of a vessel 

 so that the contained water was in constant agitation. Stems 

 placed in the vessels were whirled around making about 35 revo- 

 lutions per minute in one vessel and about 28 in the other. Very 

 little regeneration occurred (about 8 per cent), somewhat more in 

 the slower stream, slightly less in the faster one. Two days after 

 the appearanceofpolyjps they were gone, and no more regeneration 

 occurred. If the current of bubbles was stopped for 12 to 24 hours, 

 some regeneration would take place. After ten days the stream 

 was stopped altogether, and there resulted a constantly increasing 

 number of hydranths. Whirling stems through water at a com- 

 paratively rapid rate affects regeneration in practically the same 

 manner as contact, already discussed. 



Contact IS unfavorable to and more or less suppresses the develop- 

 ment of polyps. It matters little whether branches touch each other, 

 or collide with a solid object, or zuhether contact is due to growth 

 within a confined space. In the latter case there is an increasing 

 pressure proportional to the amount of growth. Contact may be 

 reinforced by pressure resulting from the weight of a superim- 

 posed layer of wet cotton; or contact may be the impact result- 

 ing from the whirling of stems through water. Whatever the 

 nature of the contact or pressure or weight or impact, regeneration 

 of polyps IS inhibited in proportion to the degree of pressure, weight, 

 impact, etc. 



EFFECTS OF LACK OF OXYGEN^^ 



Experiment 22. Sea-water was boiled to remove the oxygen 

 more or less completely from it and the amount of water evapo- 

 rated was replaced by an equal quantity of boiled tap water. An 

 equal number of stems was placed in flasks filled to the brim 

 with this deoxygenated sea-water. The smallest possible space 



"Loeb '91 and '95, Pfluger's Archiv., vol. 62. 



