284 Leonard W. Williams 



Fig. 16. Three vacuolated cells from the nucleus pulposus of an adult pig. 

 X 452. 



Figs. 17 to 20 are reconstructions of a median section of the notochord 

 and chondrostyle of embryos of the opossum, rabbit, cat and man. 



Fig. 17. From an opossum embryo of 12 mm. H. E. C, No. 616, x 1^- 



Fig. is. From a rabbit embryo of 14.5 mm. H. E. C, No. 162, X 13. 



Fig. 19. From a cat embryo of 15 mm. H. E. C, No. 437, X 12. 



Fig. 20. From a human embryo of 32 mm. H. E. C, No. 292, x "• 



