EXCRETORY ORGAN OF FKESH-WATER POLYZOA. 359 



montre avec toute ];i netteté desirable que le canal s'attache sur la 

 matrice assez |)rès de la bouche ; on voit aussi dans ces conditions que 

 son congénère aljoutit presque, sinon tout à fait, au même pt)int." 

 On tlie structure of the proximal cell, my results are identical with 



those of FOETTINGER. 



To sum up, the nephridia of Endoproctous Polyzoa are con- 

 structed on the same plan as those of mesenchymatous vvorms. They 

 are tuliular in form and consist of a row of drain-pipe cells, of which 

 the proximal one is a flanie cell. It is very evident that, from a 

 phylogenetic point of view, the so-called excretory organs of the fresh- 

 water Polvzoa have nothini>- to do A^ith these oro^ans. 



Nephridium of Fhoronis. 



The affinity of this genus with the Polyzoa proper is so great, 

 that it has been counted by some authors (Laxkester, MacIntosh) 

 among Polyzoa, as constituting the section Vermifoniiia. It should be, 

 therefore, of great importance in discussing the morphological ^'a]ue of 

 the so-called excretory organs of fresh-water Polyzoa, to give first a 

 correct representation of the ne|)hridia of Phoronis. 



The nephridia of I'lioroiiis have already been sti;died b}^ a number 

 of investigators (Dyster 185<S, Kowalevsky 1(S67, Caldwell 1S.S2, 

 MTxTOSH 1888, Benham 1889, Cori 1890). The articles by the last 

 three authors on I'lioronis, especially, deal with the subject very 

 minutely, and in some respects supplement one another, so that a fur- 

 ther investigation seemed almost unnecessary. And so it proved, for 

 my observations brought out no new facts and only confirmed the 

 statements of previous authors. 



With reo-ard to the g'eneral structure of this ortjan in Phoronis 

 psammophila, Cori writes : " Das Nephridium der Phoronis stellt 



