LATER DEVELOPMENT OP THE FROG. 657 



Fig. 3. — Horizontal section of same tadpole, still more ventral ; showing 

 first and succeeding myotomes and spinal ganglia corresponding to myotomes 

 3, 4, 5, G, and 7. Magnification 83. 



Pig. 'k^Horizontal sectiDn of 10-millimetre tadpole ; showing myotomes 

 and spinal ganglia, including the rudimentary spinal ganglion corresponding 

 to the second myotome. Magnification 50. 



Fig. 4a. — Rudimentary spinal ganglion corresponding to second myotome, 

 enlarged from Fig. 4. Magnification 800. 



Fig. 4b. — Spinal ganglion corresponding to fourth myotome, enlarged from 

 Fig. 4. Magnification 800. 



PLATE 40. 



Fig. 5. — Horizontal section of 13-millimetre tadpole; showing cartila- 

 ginous arches, myotomes, and spinal ganglia at anterior end. (Combined 

 from three sections.) For explanation of a, b and c see page 650. Magnifi- 

 cation 100. 



Fig. 6. — Sagittal section of 20-miilimetre tadpole; showing cartilaginous 

 arches, myotomes, and spinal ganglia of anterior region, and developing hind 

 'limb. (Combined from two sections.) For explanation of a, b, c, d andy see 

 page 651. Magnification 36. 



