PHYSIOLOGY OF SYNAPTULA HYDRIFORMIS 



343 



tically the same rate as in natural sea-water. Pieces of intes- 

 tine in the artificial sea-water continued to beat regularly for 

 seven hours, as long as the experiment was continued. 



Immersion in f M NaCl immediately caused a severe contrac- 

 tion throughout the entire length of the intestine. However, 

 peristalsis returned in a very few seconds, and was much more 

 pronounced than in normal sea-water. It then gradually be- 



Time for 10 

 pulsations 

 in seconds 



15 



20 25 



Temperature 



30 



35 



Fig. 1 Ordinates indicate time, in seconds, for 10 pulsations of an excised piece 

 of intestine of Synaptula; abcissae indicate temperature, Centigrade. Readings 

 taken on a single specimen. 



