1 64 GEORGE T. MCNAIR. 



a sponge which had two large oscula at a distance of about 5 mm. 

 apart was selected. A strong stimulus was applied with the 

 electrodes at the base of one chimney. The result was an 

 immediate jerk of the entire chimney followed by a gradual and 

 complete relaxation of the entire chimney from which it did not 

 recover. The other chimney was not affected. 



There is, however, a noticeable transmission of stimuli in the 

 chimney itself and the rate of this transmission is more rapid 

 from the tip to the base than from the base to the tip. This is 

 shown in the experiments with electrical stimulation and by 

 rubbing the chimney with a needle. Rubbing the edge of the 

 mouth of the osculum with a needle started a downward wave 

 of contraction which could be seen to travel at the rate of about 

 0.25 mm. per second. Rubbing at the base produced no effect. 

 Weak Faradic stimulation at the tip caused a downward wave of 

 contraction with a rate of about 0.35 mm. per second, while 

 stimulation at the base produced a slight wave of contraction 

 which traveled toward the tip at the rate of about 0.17 mm. 

 per second. 



Conclusions. 



Ephydatia fluviatilis is a fresh-water sponge which lives in 

 either quiet or flowing water. Swift currents cause a shortening 

 of the oscular chimney but do not cause a constriction of the 

 osculum. Placing the sponge in a small quantity of quiet water 

 results in a cessation of activities and death of the sponge in a 

 short time, probably because of the metabolic products which 

 accumulate in the water and poison the sponge. 



The edge of the mouth of the osculum seems to be more 

 sensitive to stimulation that the remainder of the chimney, as 

 shown by the effect of rubbing it in various places with a needle. 



Cutting the body of the sponge or sticking a needle into it 

 seemed to have no effect except the local effect on the tissues 

 which were injured. That there is no transmission of the effects 

 to surrounding tissues, even for a distance of 2 mm. or 3 mm. 

 from the injury, is shown by the continued functioning of the 

 parts as indicated by the currents coming from the oscula and 



