12 G. H. Parker 



give out excretions which in quiet water gathered to such an 

 extent in its immediate neighborhood as to cause its oscula to 

 close and only on the removal of these by a current of water would 

 the oscula open, or did the current carry oxygen to the sponge or 

 act in a purely mechanical wa}' to induce the opening of the oscula ? 

 To test these matters the following simple apparatus was con- 

 structed. Three cylindrical glass aquaria of considerable size 

 were placed at three levels so that the water from the uppermost 

 aquarium could be siphoned freely into the intermediate one 

 from which the water overflowed into the third. Having filled 

 the apparatus with seawater, it was possible to keep it running 

 continuously with the same seawater by returning that which 

 collected in the third or lowest aquarium to the uppermost one. 

 If now the current of seawater carried away excretions from the 

 sponge or brought oxygen to it and these operations had anything 

 to do with the opening of the oscula, the use of the same water 

 over and over again ought soon to brmg on a condition that would 

 no longer cause the oscula to open. But sponges placed in the 

 current of the middle aquarium remained with their oscula open 

 for hours in seawater that had been used many times over. More- 

 over the oscula closed quickly when the current was cut off and 

 reopened soon after it was started again. I therefore believe that 

 the mechanical stimulation of a current of water is an effective 

 means of opening or keeping open the oscula Stylotella. 



These first experiments were made on whole colonies of Stylo- 

 tella and only the general condition of their oscula was recorded. 

 I next turned to the individual sponges, the so-called fingers, to 

 ascertain what parts of the finger must be exposed to the current 

 to induce an opening of the osculum or the reverse. To test this 

 question I placed a colony of Stylotella in a strong current of sea- 

 water and, when the oscula were well opened, I lowered a glass tube 

 over a vertical finger so that the tube protected the whole length of 

 the finger from the laterally impinging current but was at no place 

 in contact with the finger. The water in this tube on examination 

 was found to be for the most part quiet; its condition, however, did 

 not interfere with the slight currents produced by the sponge itself. 

 Although the osculum of the finger under examination was fully 



