. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Mechanical Genesis of the Scales of Fishes. 245 Fig. 1. II III IV V VI VII. whole deptli of the body, then will somites I, IT, III, IV, V, &c. in the figure form two parallel series of muscular blocks above and below the line a, b. Each half-somite is also seen to present an acute apex directed backward at the points c and c' above and below the line a, h. The somites T, II, III, IV, and V are therefore sigmoid in outline as seen from the exterior. The myo- commata or conn
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Mechanical Genesis of the Scales of Fishes. 245 Fig. 1. II III IV V VI VII. whole deptli of the body, then will somites I, IT, III, IV, V, &c. in the figure form two parallel series of muscular blocks above and below the line a, b. Each half-somite is also seen to present an acute apex directed backward at the points c and c' above and below the line a, h. The somites T, II, III, IV, and V are therefore sigmoid in outline as seen from the exterior. The myo- commata or connec- tive-tissue septa 1, 2, 3, 4, 5, 6, &c., which intervene be- tween the somites, liave a correspond- ing sigmoid arrange- ment. The sigmoid or ^-shaped myo- commata and the myotomes are recip- rocally coadapted to each other in con- figuration, like a nest of ^ :^ ^ ^'s turned upon their sides. If we fur- ther supposed that thin- and thick-legged S^'s alternated thus—^^^^^^— we might suppose the thin-legged ones to represent tlie niyo- commata and the thick-legged ones the muscle-plates or myo- tomes. The muscular fibres of the thick-legged ^'s run longitudinally from the posterior surface of the myocomma immediately in front of it, to be inserted into the anterior face of tlie myocomma immediately behind it. The muscular tension is therefore exerted npon the opposite sides of the myocommata, and is thus propagated along the sides of the body from the head to the tail, from the first to the last myo- tome. But the tension upon the inner face of the skin is along the lines of insertion of the myocommata 1 c'c, 2 c'cj i\ c'cj &c.; this will serve to wrinkle the skin not only along the lines 1 c'c, 2 c'c^ &c., but also to cause wrinkles to appear along the dotted lines d, d', e, and e'. In this way it is easy to see that the whole lateral integument will be thrown into definitely circumscribed rhomboidal areolae, in which separate overlapping scales, s, s, s, 5,
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