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R. HATTA. 



two. It is an interesting fact that the first and second pairs originate 

 in the region where afterwards the gill-slits are formed, and they 

 disappear when the latter come into view. In later stages, the third or 

 foremost pair of persistent tubules is in close contact with the hind wall 

 of the gill-chamber. 



These facts bear a close resemblance with those in Bdellostoma as 

 described quite recently by G. C. Pbice*. Hence we have a strong 

 reason to believe that the pronephros of cyclostomata is homologous 

 with the " Nierencanälchcn " of Amphioxus as described by Th. 

 BovEiut, and that at the same time, the persistent tubules of 

 Petromyzon are homologous with those of Relachia, Teleostei, Amphibia, 

 &c. ; the mesonephros does not seem to be a part of the pronephros, 

 but it probably belongs to another series of excretory organs. 



The full paper will appear in the next number of the Journal of the 

 College of Science, Imp. Univ., Tokyo. 



June 12, 1897. 



* Price. — Development of the Excretory Organs of a Myxinoid, Bdellostoma 

 Stonti, Lockington. Zool. Jahrb., Bd. X. 



t Bovert, Th.— Die Nierencanälchcn des Ainphioxus. Zool. Jahrb., Bd. V. 



Printed October 15, 1897 



