. Elementary text-book of zoology. 172 ARCHICGELOMATA. Fig. gS.—A (Natural size).. View of oral surface showing mouth and genital pores. Notice the jointed arms. Class III.—Echinoidea (Sea-urchins).—These are spherical or oval in shape, and the calcareous skeleton forms a continuous mass of plates hearing spines. The anus opens at one pole and is sur- riSunded by five genital plates which are inter-radial. One forms the madreporite and a genital opening is situated on each. Between these there lie the smaller oculars. They bear the simple eyes and are radials. From these ten plate
. Elementary text-book of zoology. 172 ARCHICGELOMATA. Fig. gS.—A (Natural size).. View of oral surface showing mouth and genital pores. Notice the jointed arms. Class III.—Echinoidea (Sea-urchins).—These are spherical or oval in shape, and the calcareous skeleton forms a continuous mass of plates hearing spines. The anus opens at one pole and is sur- riSunded by five genital plates which are inter-radial. One forms the madreporite and a genital opening is situated on each. Between these there lie the smaller oculars. They bear the simple eyes and are radials. From these ten plates there run down orally ten double rows of plates. Those below the oculars are called the radials or ambulacrals as they bear rows of tube-feet. Those between them are inter-radials or antambulacrals. The mouth opens in the middle of a biucal membrane and is armed with five teeth. These are borne by a beautiful calcareous structure often called Aristotle's 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
Size: 1474px × 1696px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1900, bookyear1902
