Text-book of comparative anatomy . Fro. 270.—Astacus fluviatilis, section through an egg, aftercompleted formation of blastoderm, ch, Chorioii; hs, stalk ofattachment; W, blastoderm cells. The nutritive yolk is black inthis and the following Figs, (after Reichenbach).. Fio. 271.—Astacus fluviatilis, part of the surface of an eggwith embryo beginning to form.—Stage A. A Cephalic lobes,with the rudiment of the eye ; TA, thoraco-abdominal rudiments ;.GAT, formative zone of the mesoderm ; ES, endodenn disc (afterReichenbach). Stage B. Embryo, withsemicircular gastral fur-row. — Only the ventralpla
Text-book of comparative anatomy . Fro. 270.—Astacus fluviatilis, section through an egg, aftercompleted formation of blastoderm, ch, Chorioii; hs, stalk ofattachment; W, blastoderm cells. The nutritive yolk is black inthis and the following Figs, (after Reichenbach).. Fio. 271.—Astacus fluviatilis, part of the surface of an eggwith embryo beginning to form.—Stage A. A Cephalic lobes,with the rudiment of the eye ; TA, thoraco-abdominal rudiments ;.GAT, formative zone of the mesoderm ; ES, endodenn disc (afterReichenbach). Stage B. Embryo, withsemicircular gastral fur-row. — Only the ventralplate alters. At the an-terior edge of the endodenndisc a semicircular furrow,or a fold projecting Stage C. Embryo, withcircular gastral furrow.—The thoraco - abdominalplates in the middleline. The semicircularfurrow has become a fur-row round the whole cir-cumference of the eudodermdisc and is thus middle part of the en-doderm disc sinks down, sothat it now becomes a de-pression with a somewhatraised floor (gastrula inva-gination). This depressionrepresents the rudimentarymidgut, and the outer edgesof the original circularfurrow are the edges ofthe blastopore or gastrulamouth. In front of theanterior edge of the blasto
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
