. Elementary text-book of zoology. AMPHIOXUS. 301 arranged in V-shaped bars. These characteristic Vs can be seen through the skin in the Hving animal. Contraction of the myomeric muscles moves the tail from side to side, driving the animal forwards. The ventral longitudinal muscles ex- tend from the region of the mouth to the atrium. The most important skeletal organ is the notochord. It extends as a long cylindrical elastic rod from one end of the body to the other. Hence at the anterior end it passes forwards to the tip of the rostrum, in front of the brain. It consists of chordoid tissue an
. Elementary text-book of zoology. AMPHIOXUS. 301 arranged in V-shaped bars. These characteristic Vs can be seen through the skin in the Hving animal. Contraction of the myomeric muscles moves the tail from side to side, driving the animal forwards. The ventral longitudinal muscles ex- tend from the region of the mouth to the atrium. The most important skeletal organ is the notochord. It extends as a long cylindrical elastic rod from one end of the body to the other. Hence at the anterior end it passes forwards to the tip of the rostrum, in front of the brain. It consists of chordoid tissue and is enveloped in a mesoblastic sheath. Amphioxus burrows Skeletal. Fig. 215.—Transverse Section of Amphioxus behind THE Atrium. i^Ad nat.) Dorsal Subintestiiial Vein. Anal Fin (Skeleton). The dark shading is the connective tissue and the light outside is the simple ecto- derm. The section is taken across E F in Fig. 211. with its rostrum and the notochord apparently gives it the necessary solidity. It also assists the motor muscles by its elasticity. Around the notochord and nervous system and between the myomeric muscles is a continuous mass of mesoblastic connective-tissue, which at the bases of the dorsal and anal fins forms a row ol 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. Edinburgh, E. & S. Livingstone
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