. On the anatomy of vertebrates [electronic resource] . Section of yolk and embryo;Frog, magn. lxxiv. 429. DEVELOPEMENT OF BATRACHIA. 621 segments. In b, the cervical constriction begins to define thehead from the trunk: the complete coalescence of the myelonaltracts obliterates the linear trace of the median furrow, and theneurapophysial rudiments border the myelon. The embryo andits supporting yolk-mass are separated from the chorion by a clearfluid; and in the above-figured stages of developement the ciliatedepithelium begins to act upon the fluid in the direction indicatedby the arrows, pr
. On the anatomy of vertebrates [electronic resource] . Section of yolk and embryo;Frog, magn. lxxiv. 429. DEVELOPEMENT OF BATRACHIA. 621 segments. In b, the cervical constriction begins to define thehead from the trunk: the complete coalescence of the myelonaltracts obliterates the linear trace of the median furrow, and theneurapophysial rudiments border the myelon. The embryo andits supporting yolk-mass are separated from the chorion by a clearfluid; and in the above-figured stages of developement the ciliatedepithelium begins to act upon the fluid in the direction indicatedby the arrows, proceeding backward and downward along thesides: the currents are strongest on the haemal arches, from whichthe branchiae are about to be developed. In the mass of em-bryonal cells between the cephalic enlargement of the embryoand the yolk, the heart, fig. 431, r, is formed, which becomeshollow, and pulsates before the red blood appears; when thecommunication with the system of vessels is established, theheart propels blood, at first pale and with spherical corpuscles,in channels formed by liquefaction
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