. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. DEVELOPEMENT OF REPTILIA. 033 nection with the mid-pah-, as shown in fig. 332, p. 504, at a. The returning blood from the expanding lungs leads to the deve- lopement of a distinct chamber in the auricle, which finally be- comes the left auricle. Partitions in the bulbus arteriosus efl'ect a distinct communication of the pulmonary arteries with the ventricle, and a division of what now becomes ' aorta ' into two trunks. Of these one is appropriated to the left of the primitive pair of middle arches ; the other becomes the
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. DEVELOPEMENT OF REPTILIA. 033 nection with the mid-pah-, as shown in fig. 332, p. 504, at a. The returning blood from the expanding lungs leads to the deve- lopement of a distinct chamber in the auricle, which finally be- comes the left auricle. Partitions in the bulbus arteriosus efl'ect a distinct communication of the pulmonary arteries with the ventricle, and a division of what now becomes ' aorta ' into two trunks. Of these one is appropriated to the left of the primitive pair of middle arches ; the other becomes the trunk of the right arch of that pair, and also of the anterior pair in course of change into brachial and carotid arteries. The ' ductus arteriosi,' between the anterior and middle arches (fig. 332, a), arc usually absorbed (as at D, tig. 334) : those between the posterior and middle arches (d, fig. 335) are longer retained through the same course of change. The trunk, which gives off the carotids either exclusively or in common with the brachials, is posterior in Heptiles to the trunk of the left aorta, and to that of the pulmonary artery. With the dcvelopement of septa in the bulbus, there proceeds a like change in the ventricle itself, but it does not reach the condition of a complete ' sei)tum ventriculorum' until the crocodilian type of Iliematocrya is attained (figs. 339, 340). The suljstitution of kidneys for Wolffian bodies is preceded by an enlargement of the latter, tig. 443, /, at their middle part, Avith attenuation of their ends: the true kidneys begin to be formed at the upper medial part, and their uri- niferous tubes are larger and more convoluted. The genital organs appear as a narrow white band upon the ventral side of the Wolffian body. The developement of the brain closely resembles that in the Fish (pp. 604, 607), but it soon bends down at a stronger angle with the myelon. The cerebellar fold is first distino'uishable; afterwards the de- fleeted anterior p
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