. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 654 MYRIAPODA. Fig. elapsed before the body of the young my- riapod was so far liberated as to remain only partially enclosed between the two halves of the shell, as represented in Jig. 318, being still at- tached to its interior by a pe- dicle or funis (Jig. 319, d). So remarkable is its condi- tion at this period that it strongly resembles the ex- pansion of the germ in the seed of a plant, rather than the evolution of a living animal. The embryo is per- fectly motionless, and the bursting of its shell appears to
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 654 MYRIAPODA. Fig. elapsed before the body of the young my- riapod was so far liberated as to remain only partially enclosed between the two halves of the shell, as represented in Jig. 318, being still at- tached to its interior by a pe- dicle or funis (Jig. 319, d). So remarkable is its condi- tion at this period that it strongly resembles the ex- pansion of the germ in the seed of a plant, rather than the evolution of a living animal. The embryo is per- fectly motionless, and the bursting of its shell appears to be effected not by any direct effort of its own, since, up to this time, it has acquired only the form and external sem- blance of a living animal; but, by the force of ex- pansion of the growing body, the development of which being greatest along the dorsal or larger curvature, exerts, in consequence, a greater de- gree of force against the middle of the dorsal than the corresponding part of the ventral sur- face ; the head and tail of the embryo acting as a fulcrum against the ventral surface only at the ends of the shell, and thus bending it into the kidney-shaped form it assumes, while the dorsal surface of the embryo is gradually pressed through the opening. From the com- parative rapidity of its enlargement imme- diately after the shell is fissured, Mr. Newport observes, that it seems as if the stimulus given to it by exposure to a new medium, atmo- spheric air, were the great means of exciting its evolution. The embryo is now formed of eight distinct segments (Jig- 319), including the head, the ninth or anal segment being still indistinct. The head is more denned in its out- line, and firmer in texture than other parts of the body, and is inflected against the under surface of the pro- thorax (2)or second egment, from which it is divided on the upper part by a deep transverse line: at its sides it exhibits a faint trace of the future antennse. The four tho- racic segme
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