244 



THE MESODERMAL DERIVATIVES 



Olfactory pit 



Lateral append 



Epiphysis 



Anterior choroid plexus 



outh Cornified embryonic 

 teeth 



Diocoel Diencephalon 



^ qr u':d coot 

 ic'ino 

 -Lens 

 -Cornea 



-Pharyr- 



Mandibulor muscles Embryonic teeth 



4 



Hyoid cartilage 

 Dperculor chamber 



nfundibulum 



Pigmented loyer 

 ■, Optic cup 



Retina 

 Optic nerve 



Trabecular cartilage 



Rhombencepholon 



""^ \ Piluitory 

 Hypophysis 1 



Cranial nerve V 



Cranial nerves 

 VII and VIII 



Opercular Sucker 



chamber 



Hypobronchiol plate 

 Hyoid cartiloge ^1^^,^,^ gi^^d 



Anterior tip of pericordiol cavity 



Serial transverse sections of the 11 mm. frog larva. 



These veins eventually fuse and open directly into the left auricle, 

 bringing blood from the lungs after metamorphosis. 



The single abdominal vein arises as a pair of veins growing poste- 

 riorly from the sinus venosus along the ventral body wall to the level 

 of the cloaca, making junction with the femoral veins of the hind 

 legs. These paired vessels then fuse, anterior to the cloaca, into a 

 single median ventral abdominal vein. Tt then loses its connection 



