. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Embryo of the Frog. of the Frog at the earliest stage at which I have detected the motion. The vertebral canal is just closed, and at the fore part of the body three ridges on each side indicate the com- mencement of the gills. The arrows point out the course of the currents. They proceeded backwards along the dorsal surface, diverging in a direction downwards and backwards on the sides. They were visible but weaker on the abdominal surface. B represents the em- bryo farther advanced, the currents have nearly the same di
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Embryo of the Frog. of the Frog at the earliest stage at which I have detected the motion. The vertebral canal is just closed, and at the fore part of the body three ridges on each side indicate the com- mencement of the gills. The arrows point out the course of the currents. They proceeded backwards along the dorsal surface, diverging in a direction downwards and backwards on the sides. They were visible but weaker on the abdominal surface. B represents the em- bryo farther advanced, the currents have nearly the same direction but are better marked, they are strongest on the lateral eminences of the head which correspond to the future gills. In the embryo of the Newt, the phenomena are in a great measure similar; the currents seemed, however, to begin and to continue most vigorous on the abdominal surface; they are more particularly described in the paper re- ferred to. On extracting the embryo of the Frog, and viewing its surface in profile with Wollaston's doublet, moving cilia may be perceived on various parts. They appear like a transparent undulating line on the surface, and, though very minute, are so distinct as to leave no doubt of their existence. No one can fail to perceive the analogy which subsists between the phenomena just described, and those which occur in the ova of Zoophytes and Mollusca. I have not been able distinctly to perceive a rotation of the embryo of the Batrachia, as observed in the other instances, but Purkinje and Valentin state that they have seen it, and Rusconi ob- served that the embryo of the Frog, when extracted from the ovum, turned round in a certain direction, which motion he supposed to be produced by water entering and issuing through pores in the skin.* The phenomena in the Batrachian larvae have since been observed by Muller,f Raspail,J and Purkinje and Valentin.§ The last men- tioned naturalists also distinguished the cilia and perceived the motio
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