9 6 



THE STUDY OF SIX AND TEN MILLIMETER PIG EMBRYOS 



just caudal to the tuberculum impar. The ventral ends of the second 

 arches fuse in the mid-ventral plane and form a prominence, the copula. 

 This connects the tuberculum impar with a rounded tubercle derived 

 from the third and fourth pairs of arches, the anlage of the epiglottis. Its 

 cephalic portion forms the root of the tongue (Fig. 156). Caudal to the 



Pharynx 



Neuromere 4 Rathke's poucl 



Anlage of 

 tongue 



R. atrium 



Esophagus 



Interalrial 



foramen 



Lung bud 



Hepatic 

 diverliculum 



Cranial limb 

 of the intestine 



L. genital fold 



Isthmus 



M esencephalon 

 Diencephalon 



Bulbus cordis 

 Telencephalon 

 Ventricle 



Septum trans- 

 versum 



Liver 

 Yolk sac 

 Allantois 

 Tail gut 

 Cloaca 



Metanephros 



Spinal cord 



Caudal limb of intestine 

 R. mesonephros Mesonephric duct 



FIG. 96. Median sagittal dissection of a pig embryo of 6 mm., showing viscera and neural 



tube. X 1 8. 



epiglottis are the arytenoid ridges, and a slit between them, the glottis, 

 leads into the trachea. 



The branchial arches converge caudad and the pharynx narrows 

 rapidly before it is differentiated into the trachea and esophagus (Figs. 

 104 and 105). Laterally and ventrally between the arches are the four 

 paired outpocketings of the pharyngeal pouches. The pouches have each 

 a dorsal and ventral diverticulum. The dorsal diverticula are large and 

 wing-like (Fig. 104); they meet the ectoderm of the gill clefts and fuse 



