. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 622 ANATOMY OF Longitudinal scclion, Einliryo of Frog. LXXIT. obtuse as the head, the more acute and longer free part as the tail. In this growth the amiDhibian passes from a state in wliich a longitudinal section would show it supported by a spherical yolk, to that represented in fig. 431, in which the vitelline, or ' ha3mal,' portion pre- sents a semioval section, hv: it is inclosed, as in fig. 428, by the hsemal prolongations of the or- ganic layer forming the alxlominal parietes, a, and lined by the 'mu
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 622 ANATOMY OF Longitudinal scclion, Einliryo of Frog. LXXIT. obtuse as the head, the more acute and longer free part as the tail. In this growth the amiDhibian passes from a state in wliich a longitudinal section would show it supported by a spherical yolk, to that represented in fig. 431, in which the vitelline, or ' ha3mal,' portion pre- sents a semioval section, hv: it is inclosed, as in fig. 428, by the hsemal prolongations of the or- ganic layer forming the alxlominal parietes, a, and lined by the 'mu- cous ' layer, i: this be- comes differentiated as the tunics of the alimentary canal, inclosing the vitellus as the primary contents of such canal in all Batrachia. The canal now communicates with the bucco-branchial cavity; and this opens externally on the lower part of the head by a vertical fissure, on each side of which a small protuberance buds out, forming a special organ of adhesion—a pair of temporary cephalic limbs. A pair of branchiae budding out from the gill- aperture, the whole yolk being now closed in by both the in- testinal and cutaneous layers, and the tail having gained its muscular segments and cutaneous border-fin, the little tadpole, by increasing vigour of its movements, bursts the egg-mem- branes and comes forth. The external stimulus which most influences this stage is warmth. In Italy, Eusconi observed the eggs of the Frog to be hatched in four days; Bauer figures one extricating itself, in a warm spring, at Ivew, after the fifth day :' in a cold spring, it may be prolonged through four weeks. In Ahjtes ohstetricans, the developement of the 'mucous' layer proceeds to form a convoluted intestinal canal before ' extrication.' In Bana esculenta, and probably other Frogs, the vegetative organs are later in developement, and the cavity, fig. 431, liv, has not assumed the intestinal form when the embryo quits the egg: but in all Batrachia the whole yolk i
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Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1860
