. Comparative anatomy. Anatomy, Comparative. GILL POUCHES LARVA ENOODERM STRAND NEUROPORE OTIC CAPSULE NEUR- NOTOCHORD ENTE. RIC CANAL , (BLASTOPORE) POST-ANAL GUT ANUS GILL POUCHES DEFINITIVE MOUTH HYPOPHYSIS D. VERTEBRATE Fig. 249.—Diagrams illustrating the hypothetical phylogenesis of the vertebrate mouth. The primitive animal mouth, the blastopore, is converted in vertebrates either into an anus or a neurenteric canal. The definitive mouth of vertebrates therefore is a secondary mouth. But the relations of the neuropore are such that at one time in the ancestry of chordates t
. Comparative anatomy. Anatomy, Comparative. GILL POUCHES LARVA ENOODERM STRAND NEUROPORE OTIC CAPSULE NEUR- NOTOCHORD ENTE. RIC CANAL , (BLASTOPORE) POST-ANAL GUT ANUS GILL POUCHES DEFINITIVE MOUTH HYPOPHYSIS D. VERTEBRATE Fig. 249.—Diagrams illustrating the hypothetical phylogenesis of the vertebrate mouth. The primitive animal mouth, the blastopore, is converted in vertebrates either into an anus or a neurenteric canal. The definitive mouth of vertebrates therefore is a secondary mouth. But the relations of the neuropore are such that at one time in the ancestry of chordates this may have served as a mouth and the neural tube as a foregut. It is also possible that the mouth of urochordates is not homologous with the definitive mouth of vertebrates. The evidence of a paleostoma or hypophysial opening suggests that this may once have been a functional mouth. Thus the definitive mouth may have been the last in a series of four mouths. prising assumption, yet scarcely more so than many other transformations assumed by evolutionists. The digestive apparatus postulated by Delsman on the basis of the relations presented in the Amphioxus embryo has seemed to zoologists too impractical for daily use by any adult animal. The notion that the neuropore of chordate embryos represents a former. 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 Neal, Herbert V. (Herbert Vincent), 1869-1940; Rand, Herbert W. (Herbert Wilbur), 1872-1960. Philadelphia : P. Blakiston's Son
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