. Principles of modern biology. Biology. The Animal Kingdom - 663. Fig. 32-35. Structure of the common starfish. Above, left; diagram of internal structures. Below, right: the water- vascular system. (From General Zoology, by Miller and Haub. Holt, Rinehart and Winston, Inc.) portance of this perihaemal system has not been ascertained. Classes of Echinodermata. The major natural subdivisions of the phylum are: Class 1. The Asferoidea (the Starfishes). Body, star-shaped; arms, five, single or mul- tiple, not sharply demarcated from the cen- tral disc; spines, short and blunt; two to four rows o
. Principles of modern biology. Biology. The Animal Kingdom - 663. Fig. 32-35. Structure of the common starfish. Above, left; diagram of internal structures. Below, right: the water- vascular system. (From General Zoology, by Miller and Haub. Holt, Rinehart and Winston, Inc.) portance of this perihaemal system has not been ascertained. Classes of Echinodermata. The major natural subdivisions of the phylum are: Class 1. The Asferoidea (the Starfishes). Body, star-shaped; arms, five, single or mul- tiple, not sharply demarcated from the cen- tral disc; spines, short and blunt; two to four rows of tube feet, with suckers, extending along undersurface of each arm; distribution, Cambrian period to present time (Fig. 32-33). Class 2. The Echinoidea (the Sea Urchins, Sand Dollars, etc.). Body, hemispherical, disclike or egg-shaped; no arms; ossicles inter- linking and firmly sutured together; spines numerous, relatively long and movable; tube feet, numerous, with suckers; Ordovician period to present time (Fig. 32-33). Class 3. The Holothuroidea (the Sea Cu- cumbers). Body, sausage-shaped; no arms or spines; ossicles, numerous, of microscopic size; mouth, usually surrounded by retractile tentacles; Cambrian period to present time (Fig. 32-33).. 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 Marsland, Douglas, 1899-. New York, Holt, Rinehart and Winston
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