420 s. HATTA : 



peculiar and standing apart from other Vertebrata in the develop- 

 ment of the pronephros. But the results brought out in the 

 present work speak for a complete parallelism between this genus 

 and the representatives <jf other classes of Vertebrata. 



Biological Laboratory, 



The College of Peers, Tokyo. 



November, 1899. 



Postscript. 



By the kindness of Peof. Watase, I have been enabled to 

 look through Dk. Wheeler's paper on " The Development of the 

 Urogenital Organs of the Lamprey "^' which has just been published. 

 I lind a general agreement of his results with mine. The most im- 

 portant point is the discovery of the earliest traces of the pronephros 

 as given in the foregoing pages. As to the formation of the 

 segmental duct, his views are somewhat different from mine ; this 

 and some other points of divergence are, as I believe, due to 

 gaps in his materials. Thus, his fig. 1, wdiich represents section 

 through an embryo in his Stage 1, corresponds to my fig. 1, while 

 the next older stages (Stages 2 and 3) in his series, spoken of as 

 representing Goetïe's fig. 1) where the heart is already formed, 

 coincide with the oldest embryo of my Stage iv. As seen in the 

 foregoing description, most of the important processes in the 



l)Zool. Juhrbüclier, ALtlieil. für Anat. and Ontog., Bd. xiii, '99. 



