54 



general aspect of the whole tissue was less perfect. In short, 

 once having seen how preparations could be, we were no more 

 satisfied with tolerably well preserved preparations. Dendy claims 

 his sections to have been very good ; but we firmly believe that if he 

 saw our sections, he would no more be satisfied with his o wn. Th is 

 sounds rather presumptuous ; still it must be said in a case like 

 this, where — according to our opinion — the whole thing in 

 question is but a result of insufiScient preservation. 



In the not first-rate preparations we could see also a connec- 

 tion between the collars, if the cells were seen from the side. 

 But, as Dendy rightly observed, the Unes between two collars 

 are generally distinctly thicker. Dendy explains this phenomenon 

 wrongly, as stated above p. 50. 



Our conception is that these lines, uniting two neighbouring 

 collars as well as the network seen in the centre of a chamber 

 are artificial figures originating from portions of flagella and 

 collars , irregularly sticking to each other. Flagella , ciliae and 

 very delicate membranes (as the collars certainly are) habitually 

 stick together in a characteristic way if not in the very best state 

 of preservation. 



In order to study the choanocytes and especially their collars , 

 we isolated them in the way we mentioned. We thus got per- 

 fectly unshrivelled cells. Imbedding in paraffin, cutting and all 

 what is annex , even if done with the utmost care , does harm 

 somewhat. The isolated cells were still more beautifully expanded 

 than those we saw in sections. Well, the borders of the collars 

 were always perfectly sharp and intact. There was never a tracé of 

 a membrane attached to them. Suppose SoUas's membrane did really 

 exist, why should then never and never the slightest partiele of 

 it remain on the collars ? A few hours less maceration gives us new 

 proofs for our suggestion. We then find not every choanocyte iso- 

 lated, but two or three still in contact at their bases. In that case 

 there was as little to be seen of a membrane as in any other case. 



We do not intend to dweil at any length on the structure of the 

 choanocytes, nor of the flagellated chambers. We hope to do 



