. The Cambridge natural history. Zoology. ECHINUS PEDICELLARIAE 507 the head is due to the fact that there is on the outer surface of each jaw a sac-like gland developed as a pouch of the ectoderm. From it are given off two ducts which cross to the inner side of the blades and, uniting into one, run in a groove to near the tip. The gland secretes a poisonous fluid. The basal rod reaches up , p.^ per â -'â Fig. 224.âView of the apical region of Echinus esculentus, showing spines and pedi- cellariae ; drawn from the living specimen, x 3. a, Anus ; , genital pore ; i, i
. The Cambridge natural history. Zoology. ECHINUS PEDICELLARIAE 507 the head is due to the fact that there is on the outer surface of each jaw a sac-like gland developed as a pouch of the ectoderm. From it are given off two ducts which cross to the inner side of the blades and, uniting into one, run in a groove to near the tip. The gland secretes a poisonous fluid. The basal rod reaches up , p.^ per â -'â Fig. 224.âView of the apical region of Echinus esculentus, showing spines and pedi- cellariae ; drawn from the living specimen, x 3. a, Anus ; , genital pore ; i, interradius ; mp, madreporite ; per, periproct; , gemmiform pedicellaria ; pod, podia ; , tridactyle pedicellaria ; , trifoliate pedicellaria ; r, radius ; , pore for terminal tentacle of the radial water-vascular canal. to the jaws, so that this form of pedicellaria has a stiff stalk. On the inner side of each blade, near the base, there is a slight elevation (Fig. 225, B, s), consisting of cells bearing long cilia; this is a sense-organ for perceiving mechanical stimuli. The gemmiform pedicellariae are particularly abundant on the upper surface of the 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 Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipley, A. E. (Arthur Everett), Sir, 1861-1927. ed. [London, Macmillan and Co. , Limited; New York, The Macmillan Company
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
