108 EMBRYOLOGY OF THE LOWER VERTEBRATES oh. 



Fig. 60. — Portions of transverse sections through young Lepidosirens to illustrate 

 the development of the spinal nerves (ventral roots). 



A, stage 24 ; D, stage 29 -f . m, myotome ; n, nerve-trunk ; s.c, spinal cord ; sli, sheath. 



