EXCRETORY ORGAN OF FRESH-WATER POLYZOA. 355 



by CoRi. I may quote here a remark by this author and thus con- 

 clude the consideration of the subject. " Die Niere der l^ryozcm ist 

 nicht mehr selbst exkretori seh thätig, indem sie nicht selbst durch ihre 

 Epithelien gewisse Stoffe ausscheidet, sie dient vielmehr nur als ein 

 Ableitungs-organ für die mit Harnstoffen beladenen Lymphzellen." 

 CoRi supposes this condition is a product of retrogression ; I, on the 

 contrary, regard it as a ]n*imitive one from the reasons to be given at 

 the end of this paper. 



Let us now examine what we know concerning a similar structure 

 in the other group of the Ectoproctous Polyzoa. 



Excretorij Organ of Gijwnolœiuatous Polyzoa. Our knowledge of 

 the excretory organ of Gymnolaîmatous Polyzoa is next to nothing. 

 The whole literature of the subject consists of a short notice by 

 Farre (1837) accompanied by two hgures, and the remarks of 

 HiNCKS (1851) and Smitt (1866), both of whom do not go beyond 

 confirming Farre's observation. Farre found in 2Icmhmnipom 

 pilosa and Alcijonidium gelatinosum a bottle-shaped organ, ciliated in- 

 ternally, situated between the tentacles and terminating in a ciliated 

 funnel. Contrary to all the segmental organs, it lies floating in water 

 outside the body of the polypide and communicates with the body- 

 cavity only at its lower extremity. This organ is, according to Farre's 

 figures, altogether different from the structure described in the present 

 paper, so that a homology between them is out of the question. 

 Besides, all the above observations are of a comparatively early date, 

 and strangely enough, have not since been once confirmed. For 

 instance, Juliet (1880), who searched specially for this organ in one of 

 the species mentioned above, namely, Memhranipom pilosa, came only 

 to negative results. I could not find any such organ, either, in various 

 species of Scrupocellaria and Biigiila which I examined in sections. As 

 already proved by HAR:\rER, the leucocytes and the cells of the peritoneal 



