. Elementary text-book of zoology [electronic resource]. Zoology. AMPHIOXUS. 297 break up, the whole tail is resorbed, and the whole trunk rotates through nearly 180° upon its papillae. In this way the active, sensitive, highly organised " tadpole " is reduced to a quiescent, sedentary, vegetative ascidian. In Chapter VI. it is ex- plained that ontogeny may in many cases be interpreted as a repetition of phylogeny. This principle applied to the case in hand, leads us to the conclusion that the ascidians are descended from active, free-swimming, highly organ- ised Chordata^ which have
. Elementary text-book of zoology [electronic resource]. Zoology. AMPHIOXUS. 297 break up, the whole tail is resorbed, and the whole trunk rotates through nearly 180° upon its papillae. In this way the active, sensitive, highly organised " tadpole " is reduced to a quiescent, sedentary, vegetative ascidian. In Chapter VI. it is ex- plained that ontogeny may in many cases be interpreted as a repetition of phylogeny. This principle applied to the case in hand, leads us to the conclusion that the ascidians are descended from active, free-swimming, highly organ- ised Chordata^ which have degenerated on the adoption c Fig. 209.—Transverse Sec- tion THROUGH THE TaIL OF AN Ascidian Larva. (After Seeliger.) Notochord.,. a sedentary habit. AMPHIOXUS. Phylum .... Chordaia. Sub-Phylum - - - Atriozoa. Class Cephalochorda. Fig. 210.—Lateral View of Amphioxus Lanceolatus x f. (^Ad. nat.) Myomere Muscles. Dorsal 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 Masterman, Arthur Thomas; Parsons, John Herbert, Sir, 1868-1957, donor; S. H. Lazarus (Firm); University College, London. Library Services. Edinburgh : E. & S. Livingstone
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1901
