The Pharyngeal Pouches in the Mammalia 243 



diverticula ; M., moutli ; Tr., trachea ; Ao. 2-5, aortic arclaes ; D. Ao., dorsal 

 aorta ; Pul., pulmonary artery ; T. Ao., truncus arteriosus ; Tyr., thyroid ; 

 Ch. Ty., chorda tympani. x 50, reduced Vs. 



Fig. 4. — Lateral view of the pharynx in a 10 mm. pig. No. 401, Harvard 

 medical collection. D. A. 1-3, dorsal apices of first three pouches ; Gl. T., dorsal 

 process of the fourth pouch, the primordium of the glandule thyroidtenne ; 

 S. M. F., submeckelian fold ; S. T. T., sulcus tubo-tympanicus ; S. T. Ty., sulcus 

 tensoris tympani ; Ton. F., dorso-lateral region of the second pouch, later trans- 

 formed into the tonsillar recess ; V. D. 1-4, ventral diverticula ; V. F., vestibular 

 fold. X 60, reduced V^. 



Fig. 5. — Dorsal view of the pharyngeal region in the same specimen. 

 Symbols as before. X 00, reduced Vo. 



Fig. 6. — Ventral view of the same region in the same embryo. Symbols as 

 before. X 00, reduced Vo. 



Fig. 7. — Ventral view of the region of the third and fourth pouches in a 

 10 mm. pig, students' collection. Harvard medical collection. F. Pc, fundus 

 prfecervicalis ; Ph. G. 3, third pharyngeal groove ; 10, vagus ; other symbols 

 as in Fig. 8. X 80, reduced %. Figure inverted. 



Fig. S.^Dorsal view of the same region shown in Fig. 7. Ao., aorta ; 

 Car., carotid ; C. Gl., carotid gland ; D. A. 3, dorsal apex of third pouch ; 

 Gl. T., dorsal process of fourth pouch, later the glandnle thijroidicniie ; Ph. G. 4, 

 fourth pharyngeal groove, forming the inner edge of the fundus proecervicalis ; 

 S. Pc, sinus pi-recervicalis ; V. D. 2-3, ventral diverticula of second and fhird 

 pouches. X 80, reducea %. 



Fig. 9. — Lateral view of the pharynx in a 12 mm. pig. No. 518, Harvard 

 medical collection. C. GL, carotid gland ; remaining symbols as in Figs. 4-6. 

 X 60, reduced Vb- 



Fig. 10. — Dorsal view of the pharyngeal region in the same specimen. 

 D. Pr., dorsal prominence of the tonsillar fold ; F. Pc, fundus praecervicalis ; 

 V. Pc, vesicula praecervicalis ;. other symbols as in preceding figures. X 60, 

 reduced Vs- 



Fig. 11.- — Ventral view of same parts as in Fig. 10. Symbols as in preceding 

 figures. X 00, reduced Vs- 



Fig. 12. — Region of the second pharyngeal pouch in a 12 mm. pig. No. 518, 

 Harvard medical collection, viewed from below, cv., concavity on the lower 

 surface of tonsillar fold (ton. f.) ; o., ridge connecting second and third 

 pouches ; v. d. 1-2, ventral diverticula of first and second pouches, x 30. 



Fig. 13. — Region of sinus prsecervicalis in a 12 mm. pig, students' collection, 

 Harvard medical collection, ventral view. G. Nod., ganglion nodosum. Remain- 

 ing symbols as before, x 80, reduced %. 



Fig. 14. — Lateral view of the pharynx in a 14 mm. pig, No. 65, Harvard 

 medical collection. A-L. F., alveolo-lingual ridge ; C. Gl., carotid gland ; C. V., 

 concavity on ventro-lateral wall of tonsillar fold; D. A. 1-2, dorsal apex of 



