No. 2. — CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY 

 OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 

 COLLEGE, UNDER THE DIRECTION OF E. L. MARK, No. 150. 



The Development of the Mesonephros and the MilUerian Duct 



in Amphibia. 



By EoBEKT W. Hall. 



CONTENTS. 



PAGE 



I. Introduction 32 



Material and methods .... 36 

 II. Development of the mesone- 

 phros 39 



A. Amblystoma 39 



Stages I- VIII 39-47 



The dorsal extent of tiie so- 

 matic and splanchnic layers 



of the lateral mesoderm . 47 



Development of a mesonephric 

 unit in Amblystoma com- 

 pared with that in Pristiurus 49 



Later development of the me- 

 sonephric units 50 



Origin of the dorsal sets of 

 units 52 



Later development of the dor- 

 sal sets of units .... 63 



Nephrostomes of secondary 

 units 64 



Description of Table 1 and 

 Diagram 1 55 



Primary and secondary units 

 in Amblystoma and Ichthy- 

 ophis 59 



Relations between sexual and 

 secretory portions of the 

 mesonephros 61 



B. Rana 62 



Development of primary, and 



origin of secondary, bias- 



tulae 66 



Outer tubules and nephros- 

 tomes 69 



VOL. XLV. — NO. 2 



Order of appearance and num- 

 ber of primary units ... 69 



C. Comparison of the mesone- 



phric fundaments of Ambly- 

 stoma and Ichthyophis . . 71 



D. Recapitulation of the meso- 

 nephric development . . . 73 



Amblystoma 73 



Rana 75 



III. Development of the Miillerian 



duct 76 



A. Amblystoma 76 



Larvae I-XII 77-87 



B. Rana 90 



C. Hyla 94 



D. Comparison with the results 



of other writers .... 98 

 Urodela — Fiirbinger, Hoff- 

 mann, Wilson, Gemmill . 98 

 Gymnophiona — Semon . . 102 

 Anura — Hoffmann, MacBride, 



Gennnill 103 



Anmiota : Mammalia — Kip . 105 



E. Theoretical considerations . 109 



F. Recapitulation of the devel- 



opment of the Miillerian 



duct 113 



Amblystoma 113 



Rana sylvatica 115 



Hyla versicolor 116 



Addendum 117 



Bibliography 121 



Explanation of Plates 124 



