210 



THE MESODERMAL DERIVATIVES 



Table of Somites, Vertebrae, and Related Nerves of the Tadpole 



(Elliott) 



mesial margin of the somite, sclerotomal cells are proliferated off to 

 take up their positions as a continuous skeletogenous sheath around 

 the spinal cord and notochord, and between the segmental myotomes. 

 This embryonic sheath gives rise to the cartilage and finally the 

 bone of the axial skeleton. A total of nine anterior well-formed verte- 

 brae develop in this manner, alternating with the myotomes. A tenth 

 vertebra is modified into a urostyle or posteriorly elongated bony pro- 



