Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . a, adiscoid animalcule {Jig. Ill), which rapidly moved by means of tworows of vibratile cilia : the principal row being situated upon a pro-jecting ring {b\ at the margin of the disk. This ciliated body dif-fered from the gemmules of the Polypi, in being provided with amouth (e) and an anus (c), the latter occupying theapex of the cone. The course of the alimentarycanal, which extended from one to the otheraperture, was detected by feeding the little animalwith indigo.
Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . a, adiscoid animalcule {Jig. Ill), which rapidly moved by means of tworows of vibratile cilia : the principal row being situated upon a pro-jecting ring {b\ at the margin of the disk. This ciliated body dif-fered from the gemmules of the Polypi, in being provided with amouth (e) and an anus (c), the latter occupying theapex of the cone. The course of the alimentarycanal, which extended from one to the otheraperture, was detected by feeding the little animalwith indigo. In a short time the cone began toelongate and to be divided into segments, whichwere developed in four parts, the two principalpieces forming half-rings, one upon the ujjper, theother upon the lower surface, which were united bytwo shorter side-pieces. Coincident with the elon-rt^SS<r gation and segmentation of the body, was the de- \, velopment of the head from the discoid surface (a\ tmbryo ol Nereis. ^ \ y upon which first the black ocelli, and then twopointed filaments, or antennae (/), made their appearance. The. ANNULATA. 263 length of the body, and the number of segments, continued to in-crease, the disk with its vibrating cilia (6) still existing. This diskis afterwards reduced to an appendage on each side of the head, andfinally disappears. The new rings are added in front of, and notbehind, the older ones, agreeably with the order of development ofthe segments in the Bothriocephalic described in a former ring originally consists of an upper (^) and an under half-ring (Ji), analogous to the tergum and sternum in the externalskeletons of insects. The tubular and setigerous feet are lastlydeveloped from the small lateral pieces. These observations beau-tifully exemplify the repetition of structures and phenomena, charac-teristic of mature animals widely separated in the natural scale, inthe immature states of an intermediate species. With regard to the ge
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Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1850
