EXPLANATION OF FIGURES 



All the following figures of reconstructions and sections are based upon material 

 in the Embryological Collection of Columbia University with the exception of 

 Figs. q6 and 07, which are from embryo No. 21 of the Princeton Collection. For 

 permission to study and reconstruct this embryo my acknowledgements are due to 

 Professor C. W. F. McClure. 



Platfs XLI-XLII 



Figs. 1-8. Camera lucida outlines of the oral cavity of an 8.5 millimeter embryo. 

 Columbia Collection, No, 2S5. Frontal transverse sections taken at 

 intervals of 133 /a, X 80, reduced to J. 



2. Angulus oris. 



41), Lateral tongue swelling. 



41 . Tuberculum impar. 



}g. Ma.xillary process. 



61. jNIandibular process. 



67. Mandibular nerve. 



7:. Trigeminal nerve. 



-,S'. Median dorsal sulcus of pharyn.x. 



82. Nasal sulcus. 



83. Lateral nasal process. 



84. First entodermal pouch. 

 S'^. Tubotympanic sulcus. 

 87. Hypophysis. 



97. Hyoid bar. 



