. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. EMBK 1 -ONIC DE J 'EL 0PMEXT. 12.^ nerve-cord, together with the internal sheath or fascia of the muscles of the myotome, arises from the walls of a pouch-like diverticulum of myocoel which grows up be- tween the muscles and the notochord and nerve-cord. (Cf. Figs. 6"] and 6%.) The myoccel also grows downwards between the somatic layer of the peritoneum and the ecto- derm (Fig. 68). According to Hatschek the dorsal and ventral fin-spaces are
. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. EMBK 1 -ONIC DE J 'EL 0PMEXT. 12.^ nerve-cord, together with the internal sheath or fascia of the muscles of the myotome, arises from the walls of a pouch-like diverticulum of myocoel which grows up be- tween the muscles and the notochord and nerve-cord. (Cf. Figs. 6"] and 6%.) The myoccel also grows downwards between the somatic layer of the peritoneum and the ecto- derm (Fig. 68). According to Hatschek the dorsal and ventral fin-spaces are also derived from the myocoel.^ The diverticulum of the myocoel which has just been described is known as the sclerotome, since it gives rise to the fibrous sheath of the notochord and nerve-cord, which { the sheath) in most of the higher forms becomes replaced by carti- lage, and finally by bone. In the craniate Vertebrates pjg, of a transverse the sclerotome arises as a s^<=t'°" through region between atriopore and anus, of a young Amphioxus shortly solid proliferation of cells after the metamorphosis. (After Hat- from the visceral wall at the '''â '''^^l dorsal fin-space. â my. base of the somite. my. Myocii.'!. This ^'â ' Sclerotome, ao. Aorta, al. Intotine. Intercoelic membrane, Sub-in- Solid proliferation is Un- testinal vein. sp. Splanchnoca-l. doubtedly a modification of ^''"^^''^' '^"-^'"'^'='-'- a hollow diverticulum, involving, as it does, only the visceral wall of the somite, precisely as we find it in Amphioxus.'* (Cf. Fig. 33.) On their outer surface the muscles of the myotomes are not provided with a sheath of connective tissue (fascia), standing, in this respect, in contrast to the condition which obtains in the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustration
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectfishes, bookyear1894
