574 



Embryology«. Van Beneden will no doubt explain that he had 

 overlooked or forgotten the following passage from p. 330 of my me- 

 moir «On the Primitive Cell-layers« published in 1873. It would be 

 better for his reputation for accuracy and wisdom, had he not so comple- 

 tely overlooked it. »The communication of the mesoblastic 

 blood-lymph-cavity or a part of it with the exterior, 

 occurs in all Triploblastica, and is accompained by an 

 ingrowth of the epiblast, which, appearing in the sim- 

 plestworms as the pair of segmental organs or »ciliated 

 excretory tubes«, persists in all the subsequent modi- 

 fications of the type (Echinoderms , x\rthropods, Mol- 

 lusks. Vertebrates)«. This passage is quoted from the memoir in 

 which Fraipont and Van Bene den have the assurance to declare 

 that I propound the view that the urinary canals and blood-system are 

 differentiated parts of one primitive canalsystem ! 



How completely Van B e n e d e n is ignorant of what view I had 

 expressed in my memoir of 1873, and how ill-qualified therefore to 

 reply to my rectification of M. Fraipont's mis-conception, is now 

 sufficiently apparent. He is not content with telling me that he knows 

 better than I do what I Avrote, when all the time he has forgotten or 

 never read what I wrote, but he also charges me with inconsistency (!) 

 for maintaining in my »Notes on Embryology«, the view expressed in 

 the words just quoted from my earlier memoir on the »Primitive Cell- 

 layers«. He says in reference to the »Notes«: »Dans ce travail Lan- 

 kester considère les canaux urinaires comme des invaginations épi- 

 blastiqties, ce qui me parait difficile à concilier avec les idées exprimées 

 dans son premier mémoire ,0n the Cell-layers'.« 



It will be admittet that if Van Beneden had remembered the 

 passage above quoted from p. 330 of the memoir »On the Cell-layers«, 

 he could not have found any such difficulty as he says he finds, in re- 

 concihng the ideas expressed in the two memoirs. He tells us that he does 

 find such difficulty: accordingly we are justified in concluding that he 

 did not remember the passage quoted from the memoir »On the Cell- 

 layers«. But this passage is a prominent one and must be known to 

 any one who knows the memoir and more especially the views expressed 

 in that memoir as to the relationship of the body-cavity and excretory 

 apparatus of Platyhelmia. 



M. Van Beneden did not know or did not remember this pas- 

 sage. Hence I conclude that M. Van Beneden has been writing 

 about what he did not understand. 



The simple fact is that, in a very excusible way Van Beneden 

 formed a wrong conception of my views on this particular matter from 



