. Outlines of zoology. ich ingiant cuttlefish is dangerouseven to men. The inneredge of the cup margin issupported by a chitinoidring bearing small cup acts as a sucker,in a fashion which hasmany analogues, for aretractor muscle increasesthe size of the cavityafter the margin has beenapplied to some external pressure isthen greater than thatwithin the cup, and thelittle teeth keep the attach-ment from slipping. It seems likely that thearms represent a pro-podium, and the siphona mesopodium, and avalve within the siphonhas been compared to ametapodium. Skeletal system.—An
. Outlines of zoology. ich ingiant cuttlefish is dangerouseven to men. The inneredge of the cup margin issupported by a chitinoidring bearing small cup acts as a sucker,in a fashion which hasmany analogues, for aretractor muscle increasesthe size of the cavityafter the margin has beenapplied to some external pressure isthen greater than thatwithin the cup, and thelittle teeth keep the attach-ment from slipping. It seems likely that thearms represent a pro-podium, and the siphona mesopodium, and avalve within the siphonhas been compared to ametapodium. Skeletal system.—An internal skeleton is represented bysupporting cartilaginous plates in various parts of the body,especially—(a) in the head, round about the brain, archingover the eyes, enclosing the ears ; {b) at the bases of thearms; (c) as a crescent on the neck; {i) at the hook-and-eye arrangement of the mantle flap; (e) along the fringingfins. Ramified stellate cells lie in the structurelesstransparent matrix of the Fig. 217.—External appearance ofa cuttlefish {Loligo). NERVOUS SYSTEM. 405 On the shore one often finds the cuttle bone or sepio-staire, which is sometimes given to cage birds to peck atfor lime, or used for polishing and other purposes. It lieson the dorsal side of the animal, covered over by the mantlesac. In outline it is somewhat ellipsoidal, thinned at theedges like a flint axe-head, and with curved markings whichindicate lines of growth. In the very young Sepia it con-sists wholly of the organic basis conchiolin, but to this limeis added from the walls of the sac. Between the platesof lime there is gas, and though the structure may givethe cuttle some stability, it is probably of more use as afloat. Internal appearance.—When the mantle flap is cut openand reflected, the two plume-like gills are seen, and thelower end of the siphon. The dark outline of the ink-bag,followed along towards the head, leads our eyes to the endof the food canal. Near this are
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
