. Elements of zoölogy. Zoology. CHAPTER VIII. EIGHTH BRANCH OF ANIMALS. SEA-SQUIRTS (Tunicata). General Charac- teristics. — Though the adult ascidians possess little out- ward resemblance to the backboned animals, the free- swimming young (Fig. 185, a), that look like tadpoles, have a gristly cord, r, with a nerve-cord, n vy above it like the notochord that we shall see in the lancelet ; con- sequently, they are believed to repre- sent the simplest phase of backboned life. They are bag- or barrel - shaped animals, sometimes growing upon stalks; 1. Fig. 185.—Diagram of the growth of a sea- squ
. Elements of zoölogy. Zoology. CHAPTER VIII. EIGHTH BRANCH OF ANIMALS. SEA-SQUIRTS (Tunicata). General Charac- teristics. — Though the adult ascidians possess little out- ward resemblance to the backboned animals, the free- swimming young (Fig. 185, a), that look like tadpoles, have a gristly cord, r, with a nerve-cord, n vy above it like the notochord that we shall see in the lancelet ; con- sequently, they are believed to repre- sent the simplest phase of backboned life. They are bag- or barrel - shaped animals, sometimes growing upon stalks; 1. Fig. 185.—Diagram of the growth of a sea- squirt, orascidian. A, a, young free-swim- ming stage (Claveltna). a2, intermediate stage, when first settling down. B, b, full- grown sea-squirt, m, mouth; <?, hollow brain with eye; g, gill-slits ; //, heart; r, rod of gristle in free-swimming form ; nv, nerve-cord in same ; /, tail in process of absorption in intermediate form. (After Haddon.). 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 Holder, Charles Frederick, 1851-1915; Holder, Joseph Bassett, 1824-1888, joint author. New York : D. Appleton and company
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
