398 s. HATTA : 



Amphibia shows, in several respects, a parallel course with that 

 of Feiroiiiyzon. Careful observations on the development of 

 AmjDliibian pronephros, adduced by recent investigators, have 

 intensified this similarity with the exception of a few points which 

 are, however, probably of secondary importance. 



Most authors wlio have worked on the Amphibian develop- 

 ment agree in deriving the entire system of the pronephros from 

 the parietal layer of the mesoblast only, and in regarding it as 

 arising originally as a common pouch, the anterior part of 

 which is divided secondarily, l)y a partial closure of the 

 peritoneal communication, into a number of the pronephric 

 tubules. 



This view has been advanced by earlier authors such as 

 W. MÜLLER ('7Ö), GoETTE ('75), FÜebrtnger (78), Hoffmann 

 ('86), and others. The stage at which the pronephros appears 

 coincides exactly with that in Pctromyzon, as Max Füerringer 

 says in his well known work : " Die erste Entwicklung der 

 Vorniere und ihres Ausführungsganges findet hier nach der 

 Scheidung des Mesoderms in Urwirbel und Seitenplatten statt 

 und folo't unmittelbar der beo;innenden Sonderuns; der ersten in 



r5 o o 



einzelne Urwirbel amd der Spaltung der letzteren in Haut- und 

 Darmfaselplatten. Embryonen von Rana temporaria von circa 

 2.0 Mm. Länge und von Triton alpestris von ca. 2.0 Mm. L. 

 entsprechen diesen Stadium " (p. 3)^' 



MoLLiER ('90) has made out the segmental Anlage of the 

 Amphibian pronephros, having worked with the embryos of Triton, 



l)The nephrostomes are found, according to tlie author: 



2 in Sal aman drina mandata, 3 in Rnna tempnraria, 



2 in Triton alpestris, 3 in Bombinata- ignens (Goette), and 



2 in Siredon pisciformis, 4 in Coecilia rosfrata (Spengel). 



