. The anatomy of the common squid, Loligo pealii, Lesueur. Squids; Mollusks. 18 from the lower surface of the fin and, passing downward, is inserted partly on the side of the mantle and partly upon the opposite fin. The fin (text figure 8) is formed by three sets of muscle fibres, longitudinal, transverse and vertical, enclosed between three fasciae. Two fasciae are subcutaneous, forming the surfaces of the fin, and the third hes at the middle of the fin. The longitudinal muscle fibres form two thin sheets which lie upon the upper and lower surfaces of the middle fascia. They extend from one t
. The anatomy of the common squid, Loligo pealii, Lesueur. Squids; Mollusks. 18 from the lower surface of the fin and, passing downward, is inserted partly on the side of the mantle and partly upon the opposite fin. The fin (text figure 8) is formed by three sets of muscle fibres, longitudinal, transverse and vertical, enclosed between three fasciae. Two fasciae are subcutaneous, forming the surfaces of the fin, and the third hes at the middle of the fin. The longitudinal muscle fibres form two thin sheets which lie upon the upper and lower surfaces of the middle fascia. They extend from one to the other free edge of the fin. The transverse fibres arise from the obliquely inclined upper surface of the cartilage and, passing outward beneath the superficial fasciae, are inserted in them and among the muscles. These fibres are separated into long, strong and laterally compressed bundles by the short, vertical muscle fibres which, extending from the superficial fasciae to the middle fascia, form wall- like septa that extend from the base to the free edges of the fin. The bundles of transverse fibres become more slender as they approach the free edge of the fin. This is due partly to the loss of fibres by insertion and partly to the branching of the bundles. This reduction of the muscle bundles as they approach the free edge of the fin is partly counterbalanced by the union of bundles with one another. The septa of vertical fibres become thinner, less high, and more numerous near the free edge. Each septum is from Yg to 74 as thick as the bundles which it separates. As its fibres approach the middle fascia they diverge to pass between the longitudinal muscle-fibres, and hence the septum seems broader near the fascia. These septa appear through the trans- parent skin of the lower side of the fin as dark lines. The longitudinal, trans- verse, and vertical fibres together form a strong flexible &r which is able to make strong upward or downward strokes that instantly ch
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmollusks, bookyear191
