. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. r-r In'it; 148 DEVELOPMENT OF AM PHI OX US. The prneoral pit itself is absorbed, as it were, into the oral hood, so that it eventually loses its independent exist- ence as a pit, although the sense-organ of the pra^oral pit persists in the adult as a deep groove in the dorsal wall of the oral hood to the right of the base of the notochord. The remaining ciliated epithelium of the original prreoral pit increases in extent,, and grows out into the finge
. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. r-r In'it; 148 DEVELOPMENT OF AM PHI OX US. The prneoral pit itself is absorbed, as it were, into the oral hood, so that it eventually loses its independent exist- ence as a pit, although the sense-organ of the pra^oral pit persists in the adult as a deep groove in the dorsal wall of the oral hood to the right of the base of the notochord. The remaining ciliated epithelium of the original prreoral pit increases in extent,, and grows out into the finger- shaped tracts which we have already described as being characteristic of the inner surface of the oral hood, consti- tuting the so-called " ; {Cf. Fig. 3.) Equalisation of the Gill-slits. In the stage next succeeding that of which a ventral view is given in Fig. 80, the first eight primary slits — that is to say, from the original second to the ninth inclusive — C5IBi"T7s;j,:., i?;^'?!?",'^''-"*"* V Pb. m Fig. 84. — L;irv:i t()\\;ird iIr- cIdsl- of the metamorphosis, from the left siili. (After \:v.) o. Olfactory jiit. v. W'liim. lVripharynt:;e;il band. e. Endostyle. Second primary slit, the first liavinfr closed up. w. Left metapleur. Floor of atrium. ^-. /..r'^. \'estiges of thf: twelfth ami thirteenth primary slits. have become definitely established on the left side, their longitudinal and vertical axes are equalised, and in most of them the tongue-bars are completely formed (Fig. 84). No tongue-bar is formed in the first slit on either side, and this slit apparently remains as a rule simple throughout life. m. 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 Willey, Arthur, 1867-1942. New York; London : Mcmillan
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectfishes, bookyear1894
