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observers, at once made it possible to say .here nephridium ends and 

 here coelom begins'. 



B Ü t s ch 1 i 's observations have been extended and confirmed in an 

 important way by M. Fraipont. At the same time I should wish to 

 point out that he has (as it seems to me) mistaken and misrepresented 

 my statements on the subject. He says with reference to my views »il 

 considère l'appareil excréteur des Trématodes et des Cestodes comme 

 homologue de la cavité du corps des autres vers«. M. Fraipont's 

 error consists in his attributing to me the view that the entire canal 

 system of the Flat-worms is to be regarded as coelom and only the 

 pore as excretory organ or nephridium, whereas what I have maintained 

 is that while »the first portion« of the canal system is to be regarded as 

 nephridium or excretory organ a second portion (»main portion«) is to 

 be regarded as coelom. The extremely fine networks formed by the 

 canal system in As2ndogaster , terminating as it appeared to me in an 

 intercellular net-work and also the extremely fine reticulum of canals 

 in Caryophyllaeus which I had studied (with less success than has 

 M. Fraipont), were what I had especially in view in comparing the 

 main part of the canal -system of the Flat-worms to the canalicular 

 body-cavity of such a Mollusc as Phyllirhoë which communicates 

 through the pericardium by a ciliated canal, the nephridium, to the 

 exterior. 



I considered it probable, not that intracellular nephridial canals 

 were the equivalents of the coelom of Phyllirhoë^ as M. Fraipont 

 would make me state, but that the ultimate ramifications of the 

 canal-system were inter-cellular, and like the sinus system of a Mol- 

 lusc equivalent to coelom. 



This is exactly what Professor Biitschli and M. Fraipont 

 have shewn to be the fact. At the same time I fully admit that the 

 fine canals of the excretory (nephridial) system have been shewn by 

 M. Fraipont to extend further and to a greater degree of subdivision 

 and minuteness than I had supposed to exist, and that the ciliated 

 funnels are placed in most of the instances described by him upon 

 canals so fine and minute as to have escaped previous observation, and 

 that, except perhaps in Aspidogaster, I had not clearly seen the true 

 inter- cellular spaces of the coelom as now made known by him. 



The exact limitation of nephridial canals and coelomic spaces is 

 by Fraipont's results shifted to a further point on the canal system 

 than I had, in the absence of precise observations, considered probable, 

 but the substantial truth of the general conception of the Flat-worms 

 which I put forward as coelomate animals with a reduced coelom com- 

 municating by canals with the exterior, is in consequence of M. Frai- 



