Development of the Notochord 283 



EXPLANATION OF FIGURES. 



Figs. 1 to 3 are photographs of the same magnification of similar frontal 

 sections of pig embryos of 7.8, 9, and 12 mm. The notochord, the spinal 

 nerves, the intersegmental vessels, the loose tissue of the vertebrae and the 

 dense tissue of the "scleromere" should be noted. 



Fig. 1. 7.8 mm. pig embryo, section 381, Harvard Embryological Collec- 

 tion, No. 430, X 306. 



Fig. 2. 9 mm. pig embryo, section 595, H. E. C, No. 54, X 306. 



Fig. 3. 12 mm. pig embryo, section 562, H. E. C, No. 6, x 306. 



Figs. 4 to 7 are photographs of median sagittal sections of vertebrae of 

 pig embryos of 14, 20, 24, and 75 mm. 



Fig. 4. Fourth dorsal vertebra, embryo of 14 mm. H. E. C, No. 66, section 

 184, X 133. 



Fig. 5. First dorsal vertebra, embryo of 20 mm. H. B. C, No. 60, section 

 24S, X 110. 



Fig. 6. Fifth vertebra, embryo of 24 mm. H. E. C, No. 63, section 28, 

 X 76. 



Fig. 7. Eleventh dorsal vertebra, embryo of 75 mm. x 30. 



Fig. S. The nucleus pulposus and portions of the anmihts fihrosus and 

 of the epiphyses of an adult pig. X 1^- 



Figs. 9 to 12 are photographs of median sagittal sections of vertebrae of 

 embryos of the rabbit, opossum, cat and man. 



Fig. 9. Twelfth dorsal vertebra of a rabbit embryo of 29 mm. H. E. C, 

 No. 171, section 182, x 60. 



Fig. 10. Fourteenth dorsal vertebra of an opossum embryo of 12 mm. 

 H. E. C, No. 616, section 196, X 112. 



Fig. 11. First dorsal vertebra of a cat embryo of 39 mm. H. E. C, No. 

 394, section 195, X 56. 



. Fig. 12. Eighth dorsal vertebra, human embryo of 32 mm. H. E. C, No. 

 292, section 176, X 56. 



Fig. 13. Nuclei, which are possibly undergoing amitotic division, from a 

 vertebra of a pig embryo of 12 mm. H, B. C, No. 5, section 894, x 1000. 



Fig. 14. Third dorsal vertebra of a sheep embryo of 26.1 mm. H. E. C, 

 No. 1112, section 235, X 36. The trilobate character of the intervertebral 

 notochordal enlargement is shown. 



Fig. 15. Notochordal syncytium with mucin-filled spaces from a pig 

 embryo of 150 mm. x 800. 



