1075 



necessarily onlj be expelled into exciirrent canals. The vacuoles, in 

 order to attain this purpose, show a remarkable phenomenon; but 

 for briefness' sake I will not describe it here. These vacuoles can 

 be found, in my opinion, anjv\'here at arbitrary points of the 

 excurrent canal walls. 



Fig. 6. Defecation and excretion by a vacuole situated in the canal-wall. 

 The cell in which the vacuole occurred, is not drawn. (Magnification about 

 400 times). 



In addition to these defecation-places, definite deposits of feces 

 are to be found very often in the immediate neighbourhood of the 

 apopyle of the flagellated chambers. Whilst on the one hand, as I 

 have pointed out, new feces (carmine for instance) are con- 

 tinuously brought to such a deposit by means of the layer of cir- 

 culating protoplasm situated on the prosopylar side of the flagellated 

 chamber (fig. 4 : 1 —2 — 3), a large fecal conglomerate on the other 

 hand is occasionally seen to be extruded from this place of deposit 

 into the excurrent canal (fig. 4). If we now further consider what 

 was said above concerning the capture and the removal, by this 

 protoplasmic layer, of coarse particles which stop up the prosopyles, 

 we obtain an insight into a (indispensable !) system o/ cleansing of 

 the sponge, v^hich acts very rapidly. 



