630 Proceedings of Royal Society of Edinburgh. [sess. 
xxiii. Chun, Festschr. fur Leukhart , 1892. 
xxiv. Campton, Arch. f. Entwick. Meehan ., vol. iii. 
xxv. Wetzel, “ Inaug. Dissert.,” Berlin, 1896. 
xxvi. Roux, Virchow’s Arch., cxiv., and papers in Arch. f. 
Entwick. Mechanik. 
xxvii. Herlitzka, Arch. Entioick. Meehan., Bd. iv. 
xxviii. Endres and Walter, Arch. Entivick. Meehan., Bd. ii. 
Endres, Jahresbericht der Schlesischen Gesellschaft fur 
Vaterldnclische Cultur., 1895. 
xxix. Assheton, R., Journ. Anat. Phys ., xxxii., part, iii., 1898. 
xxx. Windle, Journ. Anat. Phys., xxiii., 1889. 
EXPLANATION' OE PLATES. 
Plate I., fig. A. — Whole embryo, x 18 D. 
Plates I., II., and III., figs. 1-8, represent typical members of the 
series, arranged in serial order, x 100 D. 
Plates III. and IV., figs. 9-14, represent sections through the 
posterior end of the embryo, serially arranged, x 350 D. 
