390 s. HATTA : 



this place, not go further, but return in future pages to the 

 discussion of this point. It is, however, safe, I believe, to regard 

 this portion of the mesoblast as a part of the somite. 



A'^AN" Wyhp: found the foremost pronephric segment in the 

 third body-somite (his Rumpfsegment), and IIabl states that the 

 Vornierenwulst begins in the seventh somite formed (his 

 Gesammtsegment). According to Rabl, however, vax Wyhe's 

 third Rumpfsegment corresponds to his seventh Gesammtsegment. 

 To verify this fiict Rabl has extended the comparison over 

 Peiromyzon, and found that in this case also the pronephros 

 begins in the seventh somite ; but the pronephric tubule in that 

 somite is, as noticed above (p. 380), not the anteriormost of the 

 tubules in his sense, but of the persistent tubules. 



Vais^ Wyite noticed hv^e of the pronephric segments for 

 Raja, and three for ScylUiün and Pristiurus ; while Rabl counted 

 eight Yornierenwiilste for Raja, and four for Pristiurus, The 

 results in Petromyzon, therefore, best agree with those made out 

 by RÜCKER T in Torpedo. 



The authors agree in deriving the collecting duct from the 

 lateral extremities of the pronephric Anlagen, where they 

 become confluent. 



RuCKERT has observed, in Pristiurus, as well as in Torpedo, 

 the secondary connection of the Segmentalwulst with the epiblast, 

 which has led him to believe in some contribution of epiblastic 

 cells to the formation of the pronephros, while vax Wyhe 

 and Rabl deny tliis. I have found the same connection in 

 Petromyzon, but I have found no sign of the contribution 

 of epiblastic cells to the formation of the pronephros. The 

 phenomenon is temporary in both Selachia and Petromyzon ; 

 it takes place in Selachia, according to RÜckert, in his Stad. ir, 



