573 



bulk the nephridium of an earthworm) to be the homologue of the ex- 

 cretory organs of other worms and of Molluscs and quite distinct in 

 character and origin from the distal portion of the so-called excretory 

 apparatus of the Trematods and Cestods. It was this distal portion 

 which I held to be the canalicular representative of the coelom of other 

 worms. The exact termination of the excretory canal system in any 

 Flat- worm had not been determined when I wrote, but in common 

 with others I did not suppose that the canals ended blindly, where ob- 

 servation of their further course became difficult. My observations led 

 me to hold that they terminated interstitially and to make the compa- 

 rison of this part of the so-called excretory apparatus with the blood- 

 system of a Mollusc. I am naturally therefore more likely than another 

 to appreciate and admit the value of M. Frai pout's researches, but I 

 can not allow him or M. Van Bene den to misrepresent me. 



M. VanBeneden in spite of my courteous attempt to explain 

 M. Fraipont's mis-conception of what I have written, persists that 

 he knows better than I do myself Avhat I wrote and what I meant by 

 what I wrote. This I can not allow and once for all I must beg to 

 assure Van Beneden that he is labouring under a delusion. He 

 writes : »Quelle est la théorie de L a n k e s t e r dans son premier travail ? 

 C'est que le système sanguin ou comme il l'appelle le système sanguino- 

 lymphatique des animaux triploblastiques, — qu'il soit formé de la- 

 cunes, de canaux ou de larges cavités, et les canaux urinai res, 

 quelque soit leur forme, sont des parties plus ou moins complè- 

 tement difierenciées et séparées d'un seul et même système d'espaces 

 lacunaires«. Again he says : »C'est une question ultérieure de savoir, si 

 les canaux aquifères et les espaces lymphatiques sont des parties diffé- 

 renciées d'un seul et même système lacunaire. Lankester professe 

 cette manière de voir«. 



In reference to this I have simply and plainly to say that Van 

 Beneden is as wrong as he possibly can be. He has not read or if he 

 has read he has singularly forgotten the contents of that »premier tra- 

 vail« to which he refers. The complete inaccuracy of Van Beneden 

 sufficiently explains and excuses that of his pupil Fraipont, but I 

 must say that I sincerely regret that my friend should have compelled 

 me to write publicly a second time on the subject. In this same »pre- 

 mier travail«, pubUshed in the Ann. and Mag. Nat. Hist. 1873. so far 

 from confounding »urinary canals« with any part of the blood-lymph 

 system or supposing that the two are more or less completely differen- 

 tiated parts of one and the same system of lacunar spaces, I have main- 

 tained (whether rightly or wrongly), that the urinary canals are epi- 

 blastic invaginations, as I have done at a later period in my »Notes on 



