Reactions of Sponges 1 5 



and at such lengthy periods after the apphcation of the stimulus 

 that no rehance could be placed on them. 



So far as my observations on mechanical stimulation go and 

 they are full only in reference to currents, it is quite clear that an 

 osculum closes quickl}^ (in from about three to eight minutes) in 

 quiet seawater or air, and opens more slowly (in from about seven 

 to fourteen minutes) in a current of seawater. The fact that the 

 oscular closure is quick and its opening relatively slow supports 

 the view that I have already advocated from the standpoint of the 

 structure of these parts, namely, that the sphincter? are myocytic 

 and work against the general elasticity of the surrounding tissues. 

 Hence closure might be expected to be rapid and expansion rela- 

 tively slow. 



b. Injury 



In making preparations of Stylotella for physiological tests it 

 became quite apparent thattheclosingoftheosculum was a common 

 accompaniment of cutting the sponge. If a finger of Stylotella is 

 cutoff about a centimeter from the osculum, that aperture even in 

 a current of seawater is likelyto close within a short time and to 

 remain closed for an hour or more. The occurrence of an oscular 

 closure is much less likely, if the finger is cut off at two centimeters 

 from the osculum than at one centimeter. If the cut is made at 

 half a centimeter from the osculum that opening closes very 

 quickly and may remain so for as much as a day. 



If a finger instead of being cut off, is only cut into one on side, 

 there is less likelihood of contraction than in the preceding cases. 

 A finger cut into on one side at one centimeter from the osculum 

 retained an open osculum, and the same was true when the cut was 

 half a centimeter from the osculum. But when a cut was made 

 three millimeters from the osculum, this aperture closed in nine 

 minutes and remained so over a quarter of an hour. 



If a pin is stuck into a finger of Stvlotella, its influence on the 

 osculum depends on the distance it is from that aperture. At one 

 and a half centimeters no certain response was observed, but at 

 half a centimeter the osculum closed in about ten minutes and 

 remained so several hours, though it eventualh' opened. This 



