184 



SYSTEMATIC ZOOLOGY FOR TEACHERS. 



whip-like cilia are in constant motion and these movements cause the water 

 to bs drawn in through the excurrent tubes and pass around through the 

 chambers and their connecting tubes into the excurrent, or cloaical, tubes. 

 In passing out into this large tube the water is prevented frcm returning by 

 sphincter valve which can be opened or closed at the will of the sponge. 



As particles of food pass the whip-like organs, they are captured by 

 them. Then the whip is suddenly withdrawn 'into the collar, carrying the 



Fig. 86. 





Branching forms of sponges. 



food with it. This food then passes into the basal portion of the cell 

 where it is digested. The refuse matter is thrown out of the excurrent tubes. 

 This constitutes the digestive system of the sponge. 





