OF THE MULLEEIAN DUCT OF AMPHIBIANS. 523 



or lateral wall ; in the curve from the dorsal to the ventral ■position no diverticulum 

 and no splitting appear ; in the lateral region a new diverticulum is found, and the 

 epithelial plate loses its inner connection. 



Extensive growth of the body-walls is shown by the greatly altered relations of 

 parts, and probably is the cause of these curious processes. 



Groivth Backwards. 



There are four distinct views as to the backward growth of the Mullerian duct in 

 vertebrates : it has been held to arise throughout its whole length by splitting from the 

 segmental duct, or by independent development in the epithelium opposite the 

 segmental duct ; it has been said to grow back, without help of either segmental duct 

 or epithelium, from the first Anlage ; and it has been suggested that such backward 

 growth was assisted by either the epithelium or the segmental duct. The opinions as 

 to the formation of the posterior end of the Mullerian duct in Amphibians are 

 conflicting. 



What Furbringer says on the subject has already been referred to. He thought 

 there was splitting throughout the whole length. 



Hoffmann was emphatic as to the non-participation of the segmental duct in 

 the formation of the Mullerian duct, except near the anterior end. He writes : " Ich 

 habe mehrere Embryonen untersucht bei welchen sich der Muller'sche Gang neben dem 

 Mesonephros iiber eine oft bedeutende Strecke augelegt hatte, aber weder beim 

 Mannchen (Rana, Bufo) noch beim Weibchen (Rana, Bufo, Alytes) habe ich je eine 

 Verschmelzung des Miiller'schen Ganges mit dem Wolff'schen Gang gesehen. Einmal 

 angelegt entwickelt sich also der Muller'sche Gang nach hinten selbstandig weiter, und 

 zwar hochst wahrscheinlich unter direkter Betheiligung des Peritonealepithels." 



Semon shows that in Ichthyophis the duct develops from a " Periteonalfalte " with 

 which the segmental duct shows " an keiner Stelle und auf keinem Stadium je irgend 

 welche Beziehungen." 



MacBride found the duct during development ended in a " slight thickening 

 of the peritoneum " ; and Jungersen says of the backward part of the Mullerian 

 duct that it "is seen partly to arise as a direct backward growth from the 

 anterior part, partly with participation of cells in the Mullerian cord and from the 

 epithelium." 



As to Amniota, it is interesting to observe, there is much greater difference of 

 opinion : Bornhaupt maintained independent backward growth in the case of the fowl ; 

 Waldeyer, also working with the fowl, found an ingrowing of the peritoneal epithelium ; 

 Sernoff and Gasser denied the existence of any such " Einstulpung " throughout the 

 whole length ; and Egli (rabbit) and Braun (reptiles) also saw no connection between 

 the epithelium and the backward growing tube ; Balfour and Sedgwick described in 

 the fowl three kinds of backward growth : anteriorly, independent development from 



