160 GEORGE T. MCNAIR. 



observations were made until the temperature of the water had 

 reached 40 C. At 24 the dermal membranes had taken on 

 their usual appearance, the oscula were somewhat expanded and 

 currents were issuing from them. At 34° the chimneys were 

 more extended and stronger currents were coming from them 

 than at any previous time. At 37 they were still expanded but 

 were slightly flabby and the currents were weaker. At 40 the 

 oscula had all disappeared, the dermal membranes were com- 

 pletely shriveled. None of the sponges recovered after being 

 raised to the temperature of 40 . 



Comparing these results with those obtained by Parker, it will 

 be seen that the salt-water sponge is apparently less affected by 

 temperature conditions than is the fresh- water species. With 

 Stylotella at between 9 and io° the oscula and ostia remained 

 open and the only effect seemed to be that the currents became 

 slow. At 40 there was a slight constriction of the osculum and 

 the currents gradually became slower and stopped. At 45 

 there was a flabby contraction of the oscula and the currents 

 ceased abruptly. They did not recover after being raised to 

 the temperature of 45 . 



Light. 



Neither full sunlight nor complete darkness seemed to have 

 any effect on E. fluviatilis. One large, healthy specimen was 

 placed in a dark cupboard and left there four days. At the end 

 of this time the green color due to contained algae had faded, 

 but the activity of the sponge in producing currents had not 

 diminished in any way. 



Electrical Stimulation. 



By using an inductorium with electrodes of fine platinum 

 wires, the effect of weak Faradic stimulation could be observed. 

 The electrodes were applied to three . different places: first, on 

 the side of the chimney; second, at the base of the chimney, 

 one wire on each side; third, at points on the flesh immediately 

 back of the chimney at distances of from 3 mm. to 5 mm. from 

 it. A weak stimulus when applied to the tip of the chimney 

 caused a contraction of the oscular sphincter and a gradual 



