340 ASAJIRO OKA ; OX THE SO-CALLED 



The main points in the structure of this organ were described by 

 me in No. 76 of the Zoological Magazine Vol. VII (1895), but ns 

 I have since studied various allied animals as to their excretory organs 

 and have come to conclusions that seem to ehicidate the nature of this 

 so-called excretory organ of Polyzoa satisfictorily, 1 think it will 

 be of service to publish them here, in a journal thiit enjoys a wider 

 circulation than the one above nientioned. Mv conclusions on the 

 subject are totally different from those arrived at by Coiu (1893), 

 which, owing, no doubt, to their having- been quoted by Kokschelt 

 and Heidkk in their Lflirhucli, seem at present to be the most widely 

 accepted.* 



Material and Metlwds. The colonies were first stupefied with a 

 fluid pre|)ared after the recipe of Dr. Cokt (lO'^o solution of methyl 

 alcohol in 0.75'^/„ salt solution, with ;i few drops of chloroform) and 

 then fixed with Fiemining's fluid. They were then washed in run- 

 ning water and hardened gradually in alcohol. For staining, I used 

 Bœhmer's ha'inatoxylin, sometimes in connection witli alcoh(3lic solu- 

 tion of eosin. The stupefving fluid of the Prague naturalist seems to 

 work especially well upon such forms as Polyzoa, for I was ahle by its 

 help to preserve the colonies witli every polypide fnlly protruded. As 

 noticed above, all the material I used for my study was of one species, 

 namely Fectinatella gelatinosa Oka. 



In order to compare the organ to be treated below with the 

 nephridia of allied groups, I have studied U\o other forms somewhat in 

 detail. They were Barentsia iiiisaMensis Oka and I'lioronis Kawalecskii 

 Caldwell. The farmer was collected by me in large nimibers at 

 Misaki last summer; the colonies that were f )und upon emptv tubes 



* For instance Vangel (1891), who published recently a rather popular account of the Fresh- 

 water Polyzoa of Hungary, states : — " Lei^nijabb idobeu C. J. Cori a Cristatella neumel Kiva- 

 laszt's vizedényeket talàlt, a uii a mohallatoknak a férgekhez valo kozel rokonsagara vail." 



