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XII. — The Development of the Miillerian Duct of Amphibians. By Gregg Wilson, 

 M.A., B.Sc. Edin. (With Two Plates.) Communicated by Prof. Cossar 

 Ewart, M.D., F.R.S. 



(Read 3rd December 1894.) 



Last summer I began an investigation of the Miillerian duct of Amphibians at the 

 suggestion of Professor Wiedersheim, to whom I am indebted for most kind advice 

 during the progress of my work, as well as for all the material that I have made use of 

 in the course of it. 



I have been able to examine stages in the development of the duct in Rana 

 esculenta, Triton alpestris, Salamandra atra and S. maculosa, Siredon pisciformis 

 (Axolotl), and Desmognathus ; but I have paid special attention to Salamandra atra 

 and Axolotl, which have not yet been studied in this connection. The Urodeles are 

 easier to work with than the Anura, owing to the comparatively early formation of the 

 Anlage of the Miillerian duct ; and I have found Axolotl to be particularly instructive, 

 as the pronephros and segmental duct persist during the early stages of the formation 

 of the Miillerian duct. 



I propose in this paper to describe what I have observed in various stages of the 

 development of these two forms, and to compare the results thus arrived at with the 

 appearances described in the published works on the subject. 



Literature. 



At the present time there is commonly said to be a sharp distinction in the modes 

 of development of the Miillerian duct of Anamnia on the one hand, of Amniota on the 

 other. Within the last few years, however, the difference has occasionally been called 

 in question : workers on the Amphibia have declared that they have found the duct 

 originating in the manner supposed to be proper to the Amniota ; and quite recently 

 it has been asserted that, alike in Anamnia and Amniota, the duct develops in the 

 mode generally described as characteristic of the former. The original improbability 

 that there should be two fundamentally distinct modes of origin has thus been 

 accentuated : the similarity throughout the Vertebrata is at least so great that in a 

 discussion of the Amphibia the evidence as to other forms cannot be ignored. But 

 though I shall from time to time cite the observations that have been made on other 

 groups, I shall not attempt to review the whole of the extensive literature that deals 

 with the development of the Miillerian duct. I shall merely give such a summary as 

 will show the nature of the evidence concerning the origin of the duct in the Amphibia. 



VOL. XXXVIII. — PART III. (NO. 12). 3 Y 



