244 Henry Fox 



first and second pouches ; F. Pc, fundus prsecervicalis ; Fl. P., filiform process 

 of second pouch ; Gl. T., glandule thyroidienue ; La. T., vesicle of lateral thyroid ; 

 P. T. R., posterior tympanal margin ; S. M. F., submeckelian fold ; S. T. T., 

 sulcus tubo-tympanicus ; S. T. Ty., sulcus tensoris tympaui ; Thy., thymus ; 

 Ton. F., tonsillar fold (^ sinus tonsillaris) ; Tyr., median thyroid; V. D. 2, 

 ventral diverticulum of second pouch ; V. F., vestibular fold ; y., interval 

 between vestibular and submeckelian fold, x ^0, reduced Vb- 



Fig. 15. — Dorsal view of pharyngeal region in the same embryo, ectoderm 

 shown onlj- on one side. D. Pr., dorsal prominence of tonsillar fold ; F. Pc, 

 fundus preecervicalis ; V. Pc, vesicula prpecervicalis ; other symbols as before. 

 X 60, reduced Vs. 



Fig. 16. — Ventral view of the parts shown in Fig. 15. X 60, reduced 'A. 



Fig. 17. — The region of the second pharyngeal pouch, ventral view, in a 

 14 mm. pig, No. 65, Harvard collection, a-1. f ., alveolo-lingual ridge ; fl. p., 

 filiform process of second pouch ; s. pi., sinus piriformis ; s t p., sulcus 

 tympanicus posterior. Other symbols as in Fig. 12. x 30. 



Fig. 18. — The region of the sinus prsecervicalis in a 14 mm. pig, same' 

 specimen, ventral view. D. Pc, ductus prsecervicalis ; Fl. P., ventral end of 

 filiform process of second pouch ; F. Pc, fundus prtecervicalis ; G. Nod., ganglion 

 nodosum ; Ph. P. 3, third pharyngeal pouch ; V. Pc, vesicula prajcervicalis. 

 X 80, reduced %. 



Fig. 19. — Lateral view of pharynx in a 17 mm. pig, No. 51, Harvard medical 

 collection. A-L. F., alveolo4ingual fold ; C. V., concavity on ventro4ateral wall 

 of tonsillar fold ; Cv. C, cervical cord of the thymus ; D. A. 1-2, dorsal apex of 

 first and second pouches; D. PL, dorsal plate of thymus (the carotid gland 

 is closely associated with this part, but in this specimen it was not sufficiently 

 differentiated by the stain to enable its outline to be accurately traced) ; 

 Fl. P., filiform appendix of second pouch ; F. Pc, fundus pmecervicalis ; La. T., 

 lateral thyroid vesicle, the glandule thyroidierme projects backwards from 

 its dorsal end ; S. M. F., submeckelian fold ; S. Pi., sinus piriformis ; S. T. T., 

 sulcus tubo-tympanicus; Ton. F., tonsillar fold; Thy., thymus; Tyr., thyroid; 

 V. F., vestibular fold; y., space between vestibular and submeckelian folds. 

 X 60, reduced Vb- 



Fig. 20. — Dorsal view of same parts shown in Fig. 19. S. T. Ty., sulcus 

 tensoris tympaui ; S. T. P., sulcus tympanicus posterior ; D. Pr., dorsal promi- 

 nence of tonsillar fold; C. Gl., carotid gland. X 60, reduced Vc- 



Fig. 21. — Ventral view of same parts shown In Figs. 18-19. E. Au., external 

 auditory tube; Gl. T., glandule thyroidienne. Other symbols as in Fig. 19. 

 X 60, reduced Vc- 



Fig. 22. — Region of the second pharyngeal pouch in a 17 mm. pig, No. 51, 

 seen from below. Symbols as in Figs. 12 and 17. X 30. 



Fig. 23. — Lateral view of pharynx in a 20 mm. pig. No. 542, Harvard 

 medical collection. D. A. 1, dorsal apex (recessus anterior) of tympanic 



