151 



by all its prosopyles being stopped up. Of course the sponge can- 

 not do it in any other way than by constantly making itself master 

 of those particles, by taking them up within its cells, within its 

 tissues, with the help of protoplasm current; in order to push 

 them out again afterwards (about this in another chapter (E)). 



Now, in fact I have observed this phenomenon several times 

 in my normally living microscopic preparations. 



It is known, that a choanocytic layer of a flagellated chamber 

 is covered with a thin tissue layer at the side of the incurrent 

 canal. I refer to the figures of the different authors: eg. Delage 

 (14, 16), MiNCHiN (45), YosMAER (59, 62) a. s. o. 



I myself observed in my living preparations, that outside and 

 against the flagellated chamber at the side of the incurrent canal, 

 against the base of the choanocytes, there is a thin layer of 

 apparently undifferentiated protoplasm, which one time is relatively 

 thick (1 — 3//-) and thus easily to be recognized as being separated 

 from the choanocytes (and of course from the lumen of the canal), 

 but next time is so thin, that it appears as a whole with the 

 choanocytic layer. Symbiotic algae occur but few in it, or not at 

 all. That layer, which one must imagine to be covering more or 

 less the whole prosopylar side of the chamber (except of course 

 the prosopyles), appears to be simply a continuation of the lining 

 of the incurrent canal extending over the flagellated chamber, 

 and, when visible, distinguishes itself from the choanocytic layer 

 by a lighter tint (and of course by a darker one from the lumen 

 of the canal). In that plasmic layer, now, very often all sorts of 

 particles — eg. oildroplets '), or carmine grains if the prepa- 

 ration is in a carmine suspension — are carried on slowly by 

 protoplasm current and are so removed over considerable distances 

 (eg. 7^ of the outer surface of a flagellated chamber) -). Thus 

 it is seen, for instance, that by this current carmine particles are 

 carried off aside of the chamber into the parenchyma. All this 

 is given in Fig. 72 — 74, which have been drawn from life. (In 



1) One remembers that, as mentioned ou p. 100, those oildroplets would be the 

 source of the energy in the flagellated chambers. 



2) By which a plasmic layer, which is not visible by itself, may be recognized. 



