500 EDWIN S. GOODRICH. 



endeavoured to prove exist in the majority of coelomates 

 (6, and 5, Part III). 



It follows, from the conclusion provisionally adopted above, 

 that the many theories which have been built on the assumed 

 homology between the separate segmental excretory organs 

 of Amphioxus and the renal organs of ccelomic origin of the 

 higher vertebrates must be allowed to drop for the present. 

 These latter organs (pronephros, mesonephros, and genital 

 ducts) have nothing to do with nephridia, and appear to 

 belong undoubtedly to the category of coelomostomes (5, 

 Part III, and 8). Their homologues in Amphioxus may be 

 sought in the opening of the larval " head cavities," in the 

 "brown funnels" described by Lankester, and in the segmental 

 genital sacs as already suggested by Boveri (3). It is not 

 impossible, however, that true nephridia may yet be found at 

 some stage of development amongst the craniate vertebrates, 

 and more especially in the Cyclostomes.^ 



List op Eeperences. 



1. BovEKi, T.— " Ueber die Niere des Ampliioxus," 'Miiucb. nied. Woclieu- 



schrift,' No. 26, 1890. 



2. BovEKi, T. — "Die Nierencanalchen des Amphioxus," ' Zool. Jaliib.,' 



vol. V, 1892. 



3. BovEKi, T. — "Ueber die Bildungslate der Gesclileditsdriiseii, etc.," 



' Aiiat. Anzeig.,' vol. vii, 1892. 



4. BuKGLii, O. — " Die Nemertineii," ' Fauna and Plora des Golfes von 



Neapol,' vol. xxii, 1895. 



5. GooDiucH, E. S. — "On the Nephridia of the Polycliseta," pt. i, 'Quart. 



Journ. Micr. Sci.,' vol. xl, 1897; pt. ii, ibid., vol. xli, 1898; pt. iii, 

 ibid., vol. xliii, 1900. 



6. GooDiiiCH, E. S.— " On the Ccelom, Genital Ducts, and Nephridia," 



'Quart. Journ. Micr. Sci.,' vol. xxxvii, 1895. 



7. GoojmiCH, E. S.— ;'0n the Excretory Organs of Amphioxus," 'Proc. 



Roy. Soc.,' 1902. 



^ I fully expect that nephridia will some day be found in the Enteropueusia 

 and even in the Tunicata. 



