. On the anatomy of vertebrates [electronic resource] . the crocodilian type ofHrematocrya is attained (figs. 339, 340). The substitution of kidneys for Wolffian bodies is preceded byan enlargement of the latter, fig. 443, f9 at their middle part,with attenuation of their ends: thetrue kidneys begin to be formed atthe upper medial part, and their uri-niferous tubes are larger and moreconvoluted. The genital organsappear as a narrow white band uponthe ventral side of the Wolffian body. The developement of the brainclosely resembles that in the Fish(pp. 604, 607), but it soon bendsdown at a stro
. On the anatomy of vertebrates [electronic resource] . the crocodilian type ofHrematocrya is attained (figs. 339, 340). The substitution of kidneys for Wolffian bodies is preceded byan enlargement of the latter, fig. 443, f9 at their middle part,with attenuation of their ends: thetrue kidneys begin to be formed atthe upper medial part, and their uri-niferous tubes are larger and moreconvoluted. The genital organsappear as a narrow white band uponthe ventral side of the Wolffian body. The developement of the brainclosely resembles that in the Fish(pp. 604, 607), but it soon bendsdown at a stronger angle with themyelon. The cerebellar fold is firstdistinguishable; afterwards the de-flected anterior part of the encepha-lon becomes divided into mesen-cephalon, cerebrum, and olfactorylobes, and the cerebrum speedilyattains the superiority of size whichdistinguishes the brain of the Reptile from that of the Fish. Thepineal gland shows a large proportional size in the embryo Turtle,as does also the c thalamus or lower lobe of the mesencephalon,. 634 ANATOMY OF VERTEBRATES. 444 in which the optic nerves chiefly originate: the ventricles arelarge in each mass. The eye-ball is formed, as in Fishes, by thebending of a sausage-like bag about the lens, and the coalescenceof the ends brought into contact. The cicatrix, shown in fig. 443,soon disappears. The capsule is next differentiated from the lensproper. The eye-ball is, at first, unprotected, as in Fishes ; butthe contiguous skin-border begins to encroach upon its fore part,with modified growth, to form the eyelids. After the developement of the labyrinth from the primitiveear-capsule, a tympanic cavity is formed, in which the c stapes appears as a short thick cartilaginouscylinder in the Chelonia, in which the(meatus auditorius broadens outwardsto a trumpet shape, which it retains. Inthe Ophidia the 6 stapes, fig. 444, B, e, issimilarly developed, independently of thetympanic and mandibular (or so-calledMeckels) cartilage,
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