Text-book of comparative anatomy . Fin. 100. —Three early stages of development of a Ctenophore (Callianira), after Metschnikoff,somewhat diagrammatic, cc, Ectoderm ; en, endoderm ; me, mesoderm ; d, gastric cavity ; st, oeso-phagus (stomodteum). out more and more towards the vegetative pole,which we can already observe, besides the twoprimitive germ layers, a mesodermal rudiment (B).The latter, by the invagination of the 16 macro-meres which represent the rudiment of the endo-• dermal gastro - canal systems, come to lie inside,towards the gastric cavity. Later on it reachesa position quite at
Text-book of comparative anatomy . Fin. 100. —Three early stages of development of a Ctenophore (Callianira), after Metschnikoff,somewhat diagrammatic, cc, Ectoderm ; en, endoderm ; me, mesoderm ; d, gastric cavity ; st, oeso-phagus (stomodteum). out more and more towards the vegetative pole,which we can already observe, besides the twoprimitive germ layers, a mesodermal rudiment (B).The latter, by the invagination of the 16 macro-meres which represent the rudiment of the endo-• dermal gastro - canal systems, come to lie inside,towards the gastric cavity. Later on it reachesa position quite at the animal pole, beneath theectoderm (O), its elements at the same time increas-ing by division. The ectoderm at the vegetativepole becomes depressed inwards round the blasto-pore, and thus forms a stonioclaeum (st), the rudi-ment of the cesophagus (erroneously stomach) ofthe adult Ctenophore. The mesoderm at the aboralpole, viewed from this pole, assumes the shape ofa cross. Two opposite limbs of the cross stretchout into th
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
