380 s. HATTA : 



96 and 97, to which his statement refers, represent a stage con- 

 siderably later than the first formation of the pronephros itself. 

 And the peritoneal partition is not confined to these three points, 

 but is continuous throughout the whole extent of the pronephros ; 

 moreover, beside tlie " peritoneale Scheidewände," there are found 

 two other partitions of a similar character as above stated. 

 Also, as to the fate of the structure my results differ from his : 

 I have not been able to observe at all any such contribution 

 to the formation of the hind wall of the branchial chamber and 

 of the " Venenbrücke," as is affirmed by Goette. 



Kabl ('96) says in his recent extensive work on the Selachian 

 nephric organ, that in quite young larvœ of Pelromyzon flaviatilis 

 the pronephros also begins in the seventh somite, in which the 

 first of the four ostia are found, as in Pridmruiy}^ His larvœ 

 are, however, oOl hours or 20 days and 21 hours old ; such 

 larvœ correspond to my embryos in Stage vi, and upwards, in 

 which anteriorly two pairs, and posteriorly, one pair of the 

 tubules disappeared and only three persistent tubules are seen. 

 His first nephrostome represents the foremost of the persistent 

 nephrostome. 



The accounts cited above all agree with the results given 

 in the present paper in deriving both the pronephros and the 

 segmental duct from the mesoblast alone, with the single excep- 

 tion of V. KuPFFEE, who assumes the epiblastic origin of the 

 segmental duct. They difter from the account given in the fore- 

 going pages in the mode of the formation and in the number of 

 the tubules formed. The first point of difference is due to the 



1) See the reference under Selaeliia (p. ÖUO). 



