. Comparative anatomy and physiology. 492 COMPARATIVE ANATOMY AND PHYSIOLOGY. Holothurians reduction is carried still farther, the genital tubes finally uniting into a single tube which opens near the anterior end of the body. In keeping with their other primitive characters, the Crinoidea have a more diffused arrangement of the genital glands ; these are situated in the axis of each arm, and make their way into the pinnulse that are attached to it (Fig. 205). It is ordinarily sup- posed that the generative products of all Echino- derms make their way into the water in a more or less casual ma
. Comparative anatomy and physiology. 492 COMPARATIVE ANATOMY AND PHYSIOLOGY. Holothurians reduction is carried still farther, the genital tubes finally uniting into a single tube which opens near the anterior end of the body. In keeping with their other primitive characters, the Crinoidea have a more diffused arrangement of the genital glands ; these are situated in the axis of each arm, and make their way into the pinnulse that are attached to it (Fig. 205). It is ordinarily sup- posed that the generative products of all Echino- derms make their way into the water in a more or less casual manner ; in Aste- rina, however, Lud wig has observed that the males twist their arms around those of the female, and so dispose themselves as to ensure the escaping sper- matozoa meeting with the ejected ova. A somewhat similar mode of copulation. 757 • x a. Fig. 205.— Cross Section of a Pinnule of the Arctic Feather-star (An- eschrichti) ; x 75. a. Axial cord; a', its branches ; ag, am- bulacral or food groove ; b, radial blood -vessel ; n, radial nerve; or, ovary ; pj, joint of pinnule ; w, water- vessel ; T, tentacles. (From P. H. Car- penter .slightly altered from Ludwig.) has been observed by Jic- keli in Antedon rosacea. In addition to their power of sexual multi- plication, the Echinoder- mata are distinguished by their remarkable capacity for repairing injuries, and of giving rise to new indi- viduals from separated arms • in those cases in which the rays are very numerous (Brisinga, Labidiaster),. 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 Bell, F. J. (Francis Jeffrey), 1855-1924. London, Cassell
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