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 MiXllerian Duct 



in Amphibia. 



By Egbert W. Hall. 



CONTENTS. 



PAGE 



I. Introduction 32 



Material and methods .... 36 

 II. Development of the mesone- 

 phros 39 



A. Arablystoma 39 



Stages I- VIII ..... 39-47 

 The dorsal extent of the 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 .... 53 



Nephrostomes of secondary 

 units 54 



Description of Table 1 an,d 

 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 



PAQK 



Order of appearance and num- 

 ber of primary units ... 69 



C. Comparison of the mesone- 



phric fundaments of Arably- 

 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 .... 



Urodela — Fiirbinger, Hoff- 

 mann, Wilson, Gemmill 



Gymnophiona — Semon . . 



Anura — Hoffmann, MacBride, 

 Gemmill 



Amniota : Mammalia — Kip . 



E. Theoretical considerations . 



F. Recapitulation of the devel- 



opment of the Miillerian 



duct 



Amblystoma 113 



Rana sylvatica 115 



Hyla versicolor 116 



Addendum 117 



Bibliography 121 



Explanation of Plates 124 



98 



98 

 102 



103 

 105 

 109 



113 



