Figs. M I, M II. Two sections through the head of the same embryo as fig. B. M I, the foremost of the two, passes through the anterior part of the thickening of epiblast, which becomes involuted as the auditory vesicle. It contains the rudiment of the seventh nerve, VII. Camera. (Zeiss CC ocul. 2.)
VII. rudiment of seventh nerve. au. thickening of external epiblast, which becomes involuted as the auditory vesicle. n.c. neural canal. ch. notochord. pp. body-cavity in the head. so. somatopleure. sp. splanchnopleure. al. throat exhibiting an outgrowth to form the first visceral cleft.
[47] [From the Philosophical Transactions of the Royal Society of London, Vol. CLXVI. Pt. 1. Received October 5, Read December 16, 1875.]
[48] Vide Balfour, “Preliminary account of the Development of Elasmobranch Fishes,” Quart. Journ. of Microsc. Science, Oct. 1874, p. 33. [This edition, p. [96].]
[49] Vide Balfour, “Origin and History of Urinogenital Organs of Vertebrates,” Journal of Anatomy and Physiology, Oct. 1875. [This edition, No. VII.]
[50] This commissure is not satisfactorily represented in the figure. Vide Explanation of Plate 23.
[51] [May 18, 1876.—Observations I have recently made upon the development of the cranial nerves incline me to adopt an explanation of the change which takes place in the point of attachment of the spinal nerves to the cord differing from that enunciated in the text. I look upon this change as being apparent rather than real, and as due to a growth of the roof of the neural canal in the median dorsal line, which tends to separate the roots of the two sides more and more, and cause them to assume a more ventral position.]
[52] The artist has not been very successful in rendering this figure.
[53] [May 18, 1876.—Subsequent observations have led me to the conclusion that no anterior nerve-roots are to be found in the brain.]
[54] Erste Anlage des Wirbelthier-Leibes.