• ' 169 



export of symbiotic algae (p. 52) and a contest against infecting 

 algae by ejecting them (p. 115). Especially the question about the 

 export is important. I do not venture to decide whether it can be 

 large or not; in both cases here it concerned a green sponge, so 

 a sponge that came into consideration for possessing an excess 

 of green symbiotic algae (p. 70 — 72). 



2°d. Sometimes it appears in a living sponge preparation, which 

 has first been in carmine and afterwards in pure water, that at 

 last there is still some carmine present in large conglomerates in 

 amoebocytes with numerous symbiotic algae, and such, in the rim 

 of the little sponge. This makes us suppose that, besides the 

 above mentioned defecation inside the sponge at its inner sur- 

 face, also defecation could take place at the outer surface, for 

 instance by the ordinary amoebocytes. I have not observed any 

 thing more certain, however. 



S'cl. I have never discovered pulsating vacuoles in the choano- 

 cytes, nor ever anything of defecation by these cells. 



étli. Finally a question, as I put also on p. 153: What is 

 in fact the morphological meaning of that often mentioned ap- 

 parently undifferentiated plasmic substance, which, situated in 

 the wall of the excurrent canals, proved to perform the defecation. 

 Up till now I have omitted to enter into this question purposely, 

 in order to evade unnecessarily complicating the problem of de- 

 fecation, we wanted to know in the first place. 



From the conformity of the results obtained from living- and 

 from ravel preparations (p. 161 — 164) one would immediately 

 decide, that the apparently undifferentiated substance consists of 

 amoeboid cells. Also the following supports this view : Just as I 

 described on p. 153, that I killed and macerated a living sponge 

 preparation, which had been in carmine and the contents of car- 

 mine of which I had stated, I did the same with a preparation, 

 which, according to microscopic research, was in the stage of 

 carmine defecation given on p. 163 sub 3. All cells were to be 

 seen isolated. Carmine now proved present: not or little in choa- 

 nocytes and amoebocytes with symbiotic algae, but numerous and 

 mostly in large conglomerates — and sometimes together with 



