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that 'm a separate paper. For the present we had only to state that 

 tlie choanocytes stand quite freely next to each other. They touch 

 each other only at the very base. In the sponges we have 

 gtudied , there was nothing to be seen of that groundsubstance 

 which Dr. von Leudenfeld pretends to have seen between the 

 choanocytes, nor anything of a menibrane uniting the collars, nor a 

 direct concrescence of the latter. 



Utrecht, 9 Oct. 1893. 



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