Illustrations xv 



FIGURE 



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 



61. 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 



