[74] It is very probable that in those Ophidia in which traces of limbs are still preserved, that more conspicuous traces would be found in the embryos than in the adults. [FIG. 131. CHELONE MIDAS, FIRST STAGE. _Au._ auditory capsule; _br. 1_ and _2_, branchial arches; _C._ carapace; _E._ eye; _f.b._ fore-brain; _f.l._ fore-limb; _H._ heart; _h.b._ hind-brain; _h.l._ hind-limb; _hy._ hyoid; _m.b._ mid-brain; _mn._ mandible; _mx.p._ maxillopalatine; _N._ nostril; _u._ umbilicus.] [FIG. 132. CHELONE MIDAS, SECOND STAGE. Letters as in fig. 131.] Chelonia[75]. In their early development the Chelonia resemble, so far as is known, the Lacertilia. The amnion arises early, and soon forms a great cephalic hood. Before development has proceeded very far the embryo turns over on to its left side. The tail in many species attains a very considerable development (fig. 133). The chief peculiarity in the form of the embryo (figs. 131, 132, and 133) is caused by the development of the carapace. The first rudiment of the carapace appears in the form of two longitudinal folds, extending above the line of insertion of the fore- and hind-limbs, which have already made their appearance (fig. 131). These folds are subsequently prolonged so as to mark out the area of the carapace on the dorsal surface. On the surface of this area there are formed the horny plates (tortoise shell), and in the mesoblast below the bony elements of the carapace (figs. 132 and 133). [75] _Vide_ Agassiz (No. 164), Kupffer and Benecke (No. 154), and Parker (No. 165). [FIG. 133. CHELONE MIDAS, THIRD STAGE. Letters as in fig. 131. _r._ rostrum.] Immediately after hatching the yolk-sack becomes withdrawn into the body; while the external part of the allantois shrivels up. BIBLIOGRAPHY. _General._ (154) C. Kupffer and Benecke. _Die erste Entwicklung am Ei d. Reptilien._ Königsberg, 1878. (155) C. Kupffer. "Die Entstehung d. Allantois u. d. Gastrula d. Wirbelthiere." _Zoologischer Anzeiger_, Vol. II. 1879, pp. 520, 593, 612. _Lacertilia._ (156) F. M. Balfour. "On the early Development of the Lacertilia, together with some observations, etc." _Quart. J. of Micr. Science_, Vol. XIX. 1879. (157) Emmert u. Hochstetter. "Untersuchung üb. d. Entwick. d. Eidechsen in ihren Eiern." Reil's _Archiv_, Vol. X. 1811. (158) M. Lereboullet. "Développement de la Truite, du Lézard et du Limnée. II. Embryologie du Lézard." _An. Sci. Nat._, Ser. IV., Vol. XXVII. 1862. (159) W. K. Parker. "Structure and Devel. of the Skull in Lacertilia." _Phil. Trans._, Vol. 170, p. 2. 1879. (160) H. Strahl. "Ueb. d. Canalis myeloentericus d. Eidechse." _Schrift. d. Gesell. z. Beför. d. gesam. Naturwiss._ Marburg. July 23, 1880. _Ophidia._