402 s. HATTA : 



The duct is segmental in origin. Field says : " I believe 

 I am justified in concluding that the segmental duct between 

 Somites v, and ix, arises in situ from a thickening of the somato- 

 pleure serially equivalent to that from which in the anterior region 

 the pronephros is developed " [loco cit., p. 219). There are no 

 other A'ertebrata which agree more with Petroinijzon with reference 

 to the development of the segmental duct, than Amphibia. Indeed, 

 here as there, the segmental duct is of segmental origin and is to 

 be looked upon, as seen in Petromyzon, as the continuation of 

 a series of abortive pronephric tubules in the posterior region. 



Authors who have observed the epiblastic origin of the 

 segmental duct in Amphibia are very few. vox Perexji ('87) 

 has published the results of his study on liana cscidcnta, but his 

 note is unfortunately very short'- . This view is opposed, so far 

 I am aware, by almost all recent observers. After bringing 

 the results by him into harmony with those by KÜckekt in 

 Selachia, Mollter says : " Im einen Punkte weichen die Amphibia 

 von Selachiern ab, dass die Vomiere mit dem Ektoblast in 

 keine nähere Beziehung tritt. Allerdings heftet sie besonders in 

 den Stadien, in welchen sie voluminöser erscheint, dem Ektoblast 

 oft in allallend inniger AVeise an. ''■' ''' '■' Doch lässt sich 

 stets eine scharfe Grenze beiderlei Blätter ziehen, wenigstens bei 

 Bufoj wo die Ektoblastelemente durch ihren Pigmentgehalt deut- 

 lich gekennzeichnet sind " (loco cit., p. 229). 



Tlie historical review undertaken in the foregoing pages 

 shows the agreement to a large extent of the results arrived at 

 in several groups of Anamnia. Some points of disagreement are 

 naturally met with ; but these are, I believe, only apparent. 



1)1 have not seen the jiaper ]iy I'.rouk. 



