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FIG. 7. SURFACE VIEW OF THE GERMINAL Disc OF A HEN'S EGG DURING THE LATER STAGES OF SEGMENTATION.

(Chromic Acid Preparation.)

At c in the centre of the disc the segmentation masses are very small and numerous. At b, nearer the edge, they are larger and fewer ; while those at the extreme margin a are largest and fewest of all. It will be noticed that the radiating furrows marking off the segments a do not reach to the extreme margin e of the disc.

The drawing is completed in one quadrant only ; it will of course be understood that the whole circle ought to be filled up in a precisely similar manner.

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Reference

Foster, M., Balfour, F. M., Sedgwick, A., & Heape, W. (1883). The Elements of Embryology. (2nd ed.). London: Macmillan and Co.

The Elements of Embryology (1883)

Volume 1 The History of the Chick: Egg structure and incubation beginning | Summary whole incubation | First day | Second day - first half | Second day - second half | Third day | Fourth day | Fifth day | Sixth day to incubation end

Volume 2 The History of the Mammalian Embryo: General Development | Embryonic Membranes and Yolk-Sac | Organs from Epiblast | Organs from Mesoblast | Alimentary Canal | Appendix