The works of Francis Maitland Balfour, Volume 3 (of 4)
CHAPTER III. ELASMOBRANCHII. Pp. 40-67.
Segmentation and formation of the layers, pp. 40-47. Epiblast, p. 47. Mesoblast, pp. 47-51. Hypoblast and notochord, pp. 51-54. General features of the embryo at successive stages, pp. 55-62. The yolk-sack, pp. 62-66.