152 



Fig. 74 one also sees the transport of carmine along a little 

 „bridge" bent through a canal; cnf. Fig. 70). 



That this layer of flowing plasm must exist on the incurrent- 

 canal-side of a chamber, is again very logical. For what would 

 the choanocytes, eg. in Fig. 73, do with their captured carmine, 

 if that layer was not there? 



Many times I have observed this layer on a chamber. I have 

 also had the opportunity to demonstrate it to Professor Vosmaer 

 and Professor Pekelharing. 



The rest of my observation concerned: A flagellated chamber 

 with much carmine in the choanocytes already; carmine grains 

 run up through the incurrent canal and enter by a prosopyle. 

 There approaches a large carmine ball (7 X 8 ^a), also runs 

 towards the prosopyle, but remains sticking in it. During 10 

 minutes nothing is seen to happen; but then the ball is going 

 to move and it is, along the outside of the chamber — so 

 between chamber and incurrent canal — , very slowly — as by 

 protoplasm current — carried off aside into the tissue 

 over a distance of more than 18 pt. A moment later a similar 

 phenomenon is to be observed on a somewhat smaller carmine 

 ball, at another prosopyle of the same chamber. I also observed 

 exactly the same thing happen to an alga and to a protozoon in 

 other similar preparations. 



So it is the layer of apparently undifferentiated flomng plasma^ 

 situated outside and against the flagellated chamber at the side 

 of the incurrent canal, that takes up these big particles — 

 which, carried along by the current of water, got into or against 

 the prosopyles and threaten to stop them, up perm,anently — and 

 that carries them off into the tissue, so that the prosopyles again 

 become accessible (Fig. 75). If these particles might be of any 

 use to the sponge as food, this will undoubtedly keep them and 

 carry them to the amoebocytes (and digest them); which, as we 

 saw already, also happens to the particles captured by the choano- 

 cytes. If they are of no value to the sponge, this will try to get 

 rid of them as soon as possible. More about this later on. 



