Illustrations xvii 



FIGURE PAGE 



58. Transverse Section through the Anterior 



Region of a Chick Embryo with about 

 Twenty-eight Segments. (After Minot) . 177 



59. Transverse Section through the Anterior 



Region of a Chick Embryo with about 

 Twenty-eight Segments. (After Minot) . 180 



60. Transverse Section through the Fore-Brain of 



a Chick of Fifty to Sixty Hours' Incubation 182 



6 1. The Eye of a Bird: A Sagittal Section; B 



Surface View of Entire Organ. (After Par- 

 ker and Haswell from Vogt and Yung) . 184 



62. Transverse Section through the Anterior 



Region of a Chick Embryo of about Twenty- 

 eight Segments. (After Minot) . . .186 



63. Transverse Section through the Anterior Part 



of an Embryo of Sixty-eight Hours. (After 

 Duval) 192 



64. The Head of an Embryo Chick at the End of 



the Fifth Day of Incubation, Seen from 

 Below. (After Marshall) . . . .196 



65. Diagram of the Arterial Circulation on the 



Third Day. (After Foster and Balfour) . 200 



66. Diagram of the Venous Circulation of the 



Third Day. (After Foster and Balfour) . 201 



67. Diagram of a Portion of the Digestive Tract of 



a Chick Embryo during the Fourth Day. 

 (Foster and Balfour from Gotte) . . 205 



68. Transverse Section of an Embryo of the 



Fourth Day. (After Duval) . . .208 



