3(30 ASAJIRÖ OKA; ON THE SO-CALLED 



einen bewimperten, schleifenförmig gekrümmten Knnal vor, un 

 welchem man einen absteigenden Schenkel unterscheidet, der sich 

 mittels eines offenen Flimmertrichters mit der unterhalb des Dia- 

 phragmas gelegenen Leibeshöhle in Verbindung setzt, dann einen 

 aufsteig-enden Schenkel und schliesslich ein Endstück, das mit einer 

 üettnunsf nach aussen mündet. Was die Lai^e dieser schleifenformig'en 

 Nierenkanäle im Körper anbelangt, so sehen wir, diiss dieselben hinter 

 dem Diaphragma zu beiden Seiten vom Endal)schnitte des Dünn- 

 darii es sich finden und dass sie ausserhalb der Leibeshöhle als 

 retroperitoneal gelagert sind." This applies, witli a little modifica- 

 tion as to position, to the nephridia of 7'//. Koiralccsldi also. In 

 Phoronis, the nephridia are special organs of" a tubular form, serving 

 to connect the body-cavity with the exterior. In this respect, these 

 organs may be compared with the nephridium ])roper or metanephri- 

 dium of cœlomatous animals, so-called in contradistinction to the 

 pronephridium which includes such forms as the excretory organ of 

 mesencliymatous worms or that of the Endoprocta. 



CoEi homologizes the ciliated tubes of fresli -water Folyzoa with 

 the nephi'idia of Fltowiiis, apparently without hesitation ; for he 

 assigns to the former a structure in every respect analogous to that of 

 the latter. Such a conception naturally results, it appears to me, from 

 a not sufficiently accurate interpretation of the cross sections, some of 

 which, indeed, are very liable to be misconceived. No one looking 

 at Coin's fig. 4, PI. XXIV (1890) for instance, and fig. 9 at the 

 end of this paper, would find it difficult to accept the homology 

 of the pairs of oval sections in them. A comparison of my diagram- 

 matic figures of Polyzoa with any figure of the neplu'idium of Plioronis, 

 how^ever, will show immediately that the resemblance in this case is 

 only a deception and has no value whatever in the consideration of the 

 organs in cjuestion. 



