1900] MICROSCOPICAL JOURNAL. 333 



then over the edge and down the inside till they reach 

 the body of the animal at the bottom of the funnel when 

 they are engulphed in the soft protoplasm ; the nutrient 

 material is taken up by the protoplasm, and the waste 

 matter probably excreted by means of the contractile 

 vacuoles. 



We are now in a position to understand a few more de- 

 tails about the canal system of the sponge. We have al- 

 ready learned that the water enters through minute pores 

 in the outer layer, and that, somehow or other, it finds its 

 way through the fairly thick wall into the central cavity. 

 The wall, as we have seen, is made up of the flagellate 

 chambers together with the gelatinous material and em- 

 bedded spicules which form the boundary or supporting 

 structures to the chambers, and the water passes freely 

 through the wall in a very definite course. Why does it 

 take that course ? Minute examination of the wall of the 

 flagellate chambers elicits the fact that at intervals be- 

 tween the collared cells which make up the wall small 

 holes or prosopyles occur through which water can easily 

 pass when impelled to do so by the violent movement of 

 thousands of the minute vibratile processes of the collar- 

 ed cells. This accumulated movement is the motive power 

 of the current. As the water sweeps through these tiny 

 holes and bathes the wall of the chamber studded with 

 the cells the food particles are detained by the protoplas- 

 mic collars and by them transmitted to the digestive por- 

 tion of the cell. The water thus robbed of its nutrient 

 material, and bearing with it the rejected portions of the 

 food particles, passes through the chamber to join the gen- 

 eral current which issues from the gastral cavity at the 

 top of the sponge. To summarize the course of the cur- 

 rent we may refer to its entry by the pores and so into 

 minute irregular channels, inhalent canals, which pene- 

 trate the gelatinous material and reach the wall of the 

 flagellate chambers ; then through small holes or proso- 



