Archive image from page 75 of The development of the frog's. The development of the frog's egg; an introduction to experimental embryology . developmentoffro00morg Year: 1897 60 DEVELOPMEXT OF THE FROG'S EGG [Cn. Y seen in Fig. 21, A. The anterior end of the medullary tube shows on each side a lateral protrusion, the eye-bulb. At the anterior end of the body we can see the sense-i3late and on each side the broad gill-plate. Lying in the sense-plate on each side is a deeply pigmented area which is the forecast of the 'suckers,' S. There is a depression in the middle line, in the centre of the
Archive image from page 75 of The development of the frog's. The development of the frog's egg; an introduction to experimental embryology . developmentoffro00morg Year: 1897 60 DEVELOPMEXT OF THE FROG'S EGG [Cn. Y seen in Fig. 21, A. The anterior end of the medullary tube shows on each side a lateral protrusion, the eye-bulb. At the anterior end of the body we can see the sense-i3late and on each side the broad gill-plate. Lying in the sense-plate on each side is a deeply pigmented area which is the forecast of the 'suckers,' S. There is a depression in the middle line, in the centre of the sense-plate. This depression marks the mouth-depression, and indicates the point at which, later, the stomodccal invagination will take place. (See Fig. 20, F.) Fig. -Development of embryo. Anterior view, showing sense-plate, uasal pits, stomodauim, and gills. (After Ziegler.) A later stage is shown in Fig. 21, B. The relation of the parts is much as in the last figure. The anterior end of the medullary tube is larger than before, and the protuberances of the eye-evaginations are more apparent. In the gill-plate on each side appears a vertical depression and later another de- pression behind it, GS, GS'. These depressions mark the external gill-slits. The anus has shifted to a more ventral position. The suckers have each elongated ventrally, and have fused into a pigmented V-shaped ure. The outer medullary
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