igoS.I EXCRETORY ORGANS OF METAZOA. 553 



6. Endoprocta. 



Joliet (1880) described for Pedicellina and Loxosoma a pair of 

 short ciliated canals with a common nephridiopore, and with their 

 inner ends open to the body cavity. Prouho (1890) leaves the 

 question unsettled whether these ends are open or closed. All 

 other observers describe the inner termination of each canal as 

 closed by a flame cell: so Foettinger (1887) and Ehlers (1890) for 

 Pedicellina, Harmer (1885, Loxosoma), and Davenport (1893, 

 Urnatella) . The cavity of these canals is intracellular, and only in 

 Loxosoma are there paired nephridiopores. 



Besides this " Chief excretory apparatus " Davenport found in 

 the stalk of Urnatella " elongated spaces terminating blindly at one 

 end in structures which must be regarded as flame cells ... I have 

 not, however, been able in any instance to trace an individual tubule 

 to any considerable distance, or until it opens into any other organ." 



Accordingly, all Endoprocta seem to have a pair of nephridia 

 internally closed that do not serve as genital ducts, and in one 

 genus flame cells seem to occur in the stalk. 



In regard to their development, Hatschek (1877) found in the 

 full-formed larva of Pedicellina a pair of ciliated canals like those 

 of the adult, but did not determine either their structure or origin. 

 It would seem probable that this excretory organ persists in the 

 adult. 



7. Rhodope. 



For this curious form that has been variously related to die 

 Turbellaria and the opisthobranch mollusks, Bohmig (1893) de- 

 scribed a nephridiopore on the right side just anterior to the anus, 

 into which opens a " Urinkammer " ; into the latter discharge rami- 

 fied ducts, and to each of these are attached about forty flame- 

 bearing terminal organs, each completely closed from the body 

 cavity and consisting of from four to eight cells. Nothing is known 

 of the development. 



8. ACANTHOCEPHALA. 



The excretory organs of this group are known only from the 

 observations of Kaiser (1892, 1893). They occur only in the 

 large Echinorhynchus gigas and seem to be absent in the smaller 



PROC. AMER. PHIL. SOC, XLVH. I90 JJ, PRINTED JANUARY I4, I9O9. 



