166 



the water. If the right (excurrent) canal has been found, the 

 plasma contracts and the vacuole bursts; if, however, it proves 

 to be an incurrent canal, the vacuole will withdraw to try the 

 same somewhere else. 



Now, my observation relative to this was in fact, that the 

 vacuoles withdrew from canals which, if it was possible to dis- 

 tinguish, proved to be incurrent canals. (One can distinguish it 

 from the situation of the flagellated chambers). 



We now got to know the process of defecation, which, as we 

 saw, must very often take place in nature, where the water 

 contains so many particles, that the sponges have quite a dirty 

 tint, which however they soon lose in clean water (p. 160 — 161). This 

 defecation proved to take place by means of large vacuoles. These 

 vacuoles are partly filled with liquid — undoubtedly originating 

 from the sponge tissue — ; this liquid is ejected with the feces. 

 Rave not tve found here, then, besides a powerful defecation pro- 

 cess also a strongly acting excretion process? I think we have. 



But we have not yet quite finished the process of defecation. 

 There exists, besides the here described ivay of defecation every ivhere 

 at arbitrary points of the excurrent canal ivalls, still another method 

 which, as I believe, we shall have to distinguish from the first 

 one. And this, because it is apparently' bound to a more or less 

 fixed place: 



In sponges nfed^'' on carmine one repeatedly meets with one 

 large accumulation of this matter near each fiagellated chamber, 

 and again in an apparently undifferentiated plasmic substance, in 

 the wall of the excurrent canal {Fig. 73). While, now, on the one 

 side new carmine grains are constantly added to the large heap 

 by the fiowing plasmic layer, situated at the incurrent-canal-side 

 of the chamber (p. 151, 156), one sees on the other side now and 

 then a big conglomerate being ejected from the heap into the ex- 

 current canal; both of which is represented in Fig. 73 (drawn 

 from life). I observed this, of course, again in my living tissue 

 preparations. 



Of course it cannot be said, if this accumulation of carmine — 



