. Text-book of embryology. Embryology. mes mes C^m^—^-^. Fig. 189.—Two transverse sections throngh the "ger- minal disc," or developing area of the egg of the Scorpion, Euscorpius carpathicus, in two stages. (After Brauer.) A, Stage of the formation of the serosa. B, stage of the formation of the amnion, am, beginning amnion; eci, ectoderm ; end, endodermal nuclei; mes, mesoderm ; germ, primitive germ cells, probably corresponding to the " primi- tive cumulus " of the spider's egg. Fio. 190.—Ventral view of em- bryo of the Scorpion Euscor- pius carpathicus showing segments
. Text-book of embryology. Embryology. mes mes C^m^—^-^. Fig. 189.—Two transverse sections throngh the "ger- minal disc," or developing area of the egg of the Scorpion, Euscorpius carpathicus, in two stages. (After Brauer.) A, Stage of the formation of the serosa. B, stage of the formation of the amnion, am, beginning amnion; eci, ectoderm ; end, endodermal nuclei; mes, mesoderm ; germ, primitive germ cells, probably corresponding to the " primi- tive cumulus " of the spider's egg. Fio. 190.—Ventral view of em- bryo of the Scorpion Euscor- pius carpathicus showing segments and (After Brauer.) a61"7, the rudiments of the ab- dominal appendages; c7t, rudiment of chelicera; , rudiment of the cheliceran ganglion; , cephalic groove; , caudal lobe; Zi"4, the rudiments of the walking legs ; petZ, rudiment of pedipalp; stom, open- ing of stoniodaeum ; , ganglia of the ventral nerve cord. fore telolecithal and its segmentation is meroblastic, but this type of telolecithal egg, as we can see by comparing it with the egg of the spider, must have been secondarily derived from the centrolecithal type. At a later period cells are budded off from the blastoderm which wander into the yolk. These cells, according to Brauer, eventually form the endodermal epithelium, at a much later period in the develop- ment. At the same time the edges of the blastoderm give rise to a sheet of cells which grows backwards over it and forms a protective cover for it, called the amnion. A little later, a second outer cover- ing of the same kind is formed which is called the serosa (Fig. 189).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original MacBride, E. W. (Ernest William), 1866-1940; Kerr, John Graham, 1869-; Heape, Walter, 1855-1929. London : Macmillan
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Keywords: ., bookcentury1900, bookdecade1910, bookpubli, booksubjectembryology
