A. OKA, NEPHRTDIUM OP POf.YZOA. 21 



EXPLANATION OF PLATER. 

 (—7- X 7i J— Eye-piece 1, o])jective A of a Zeiss' microscope, and drawn 

 >}' means of a camera at the height of the oliject. 

 7 



X J/ 1 =the same of a Leitz's. 



\-Y- ^ 'S' )= „ ., ,, ., Seil)evt. 



^fi:z=Eirst antenna^. 

 ^?'- = Second aiitenna\ 

 hr =Branchia. 

 I =Endite. 



On the Nephridium of Phylactolae- 

 matous Polyzoa. 



WHh PJ. IX. 



P.y A. Oka. 



Although there is a large number of naturalists who have investigated 

 fresh-water Polyzoa, only few of them seem to have noticed the existence of 

 a special organ of excretion in these animals. In 1888, when I was occupied 

 in studying a species of PectinateUa, the only literature on this organ con- 

 sisted of a few lines l)y A^erworn illustrated with two simple figures. 

 Kraepehn,^ who nearly at the same time with A^erworn, published a mono- 

 graph of German fresh- water Polyzoa, simply denied its existence. Since 

 then, two authors, namely Braem and Cori, made special researches on the 

 subject, but the results of their investigations can not on many points be 

 reconciled with one another. 



1. Kraepelin, K. Die deutschen Siisswasserliryozoeu. Eine Monoofi-apliie. Festschrift des 

 natanvissenschaftl. Vereins in Hamlmrg, 1887. 



