Mesenchyme 



Dorsal aorta 

 Pronephric duct 



Neural crest 



Dermatome 

 Myotome 



Lateral line nerve 

 Sclerotome 

 Neurocoel 

 Notoctiord 

 Post-cardinal vein 

 Sub-notochordal rod 

 Coelom 

 Somatic mesoderm 

 Splanchnic mesoderm 



Gut 

 Yolk 



Vitelline veins 



The 7 mm. frog tadpole: transverse sections. Through the mid-body level. 



Ectoderm 



epithelia 



neura 

 Sub-notochordal rod 



Nerve cord I 



Neurocoel (spinal canal) 



Notochord 



Somite 



Nephrotonne 

 (mesomere) 



Hypomere 

 (lateral plate 

 mesoderm) 



Early organogeny. The 5 mm. frog tadpole at mid-body level. Photograph 



of cross section. 



147 



