. Comparative anatomy. Anatomy, Comparative. 658 COMPARATIVE ANATOMY theory is that it derives vertebrate from invertebrate without reversing dorsal and ventral sides. Hubrecht assumes that the paired nerve cords of the Nemertean unite in the mid-dorsal line to form the nerve cord of vertebrates. The paired cere- bral lobes of the nemertean become the brain of the vertebrate. Hubrecht compares the intestinal diverticula of the flatworm with the coelomic outpocketings of the amphioxus embryo. The more anterior diverticula are possibly the Fig. 530.âDiagrams illustrating Hu- r 1 -n 1 r brecht's
. Comparative anatomy. Anatomy, Comparative. 658 COMPARATIVE ANATOMY theory is that it derives vertebrate from invertebrate without reversing dorsal and ventral sides. Hubrecht assumes that the paired nerve cords of the Nemertean unite in the mid-dorsal line to form the nerve cord of vertebrates. The paired cere- bral lobes of the nemertean become the brain of the vertebrate. Hubrecht compares the intestinal diverticula of the flatworm with the coelomic outpocketings of the amphioxus embryo. The more anterior diverticula are possibly the Fig. 530.âDiagrams illustrating Hu- r 1 -n 1 r brecht's theory of the origin of the noto- homologues of the gill pouCheS ot chord from the proboscis sheath of rhordates nemerteans. A, diagram of a nemertean, ,â â , i ⢠r j-rc B. of a chordate. The proboscis of the One of the chief difficulties in nemertean according to Hubrecht becomes making Comparison between the vertebrate hypophysis. ° vertebrates and invertebrates has been the absence in invertebrates of any structure similar to the notochord. By comparing the proboscis sheath of nemerteans with the notochord, Hubrecht thinks that he has removed this obstacle. ECTODERM CIRCULAR MUSCLES DORS NERVE-CORD LONG. MUSCLES PROBOSCIS SHEATH V-PROBOSCIS rGONAD. 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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