FOOTNOTES:
[1] The skin consists of an outer layer of epiblastic origin, the epidermis, and an inner layer of mesoblastic origin, the dermis. The epidermis is divided into two principal layers, an outer one, the horny layer or stratum corneum, and an inner one, the stratum Malpighii. The innermost part of the stratum corneum is distinguished as the stratum lucidum, and the outermost part of the stratum Malpighii as the stratum granulosum.
[2] The enamel of the pharyngeal teeth of some Teleosteans is hypoblastic in origin.
[3] See also p. 71.
[4] It is usual to regard the clavicle as a membrane bone, but Kölliker has shown that in rabbit embryos of about the 17th day it is cartilaginous.
[5] In compiling these paragraphs on Histology, free use has been made of Klein and Noble Smith's Atlas of Histology, the small Histologies of Klein and Schäfer, Huxley's Elementary Physiology, and Lloyd Morgan's Animal Biology.
[6] See Huxley's Elementary Physiology, Revised edition, London, 1886, p. 180.
[7] Strictly speaking the jaws, visceral skeleton, ribs and sternum do not form part of the axis, but it is convenient to group them as parts of the axial skeleton.
[8] F.M. Balfour, Comparative Embryology, vol. II., London, 1881, p. 465. W.K. Parker and G.T. Bettany, The Morphology of the Skull, London, 1877.
[9] Sometimes also called ectethmoids or parethmoids.