Text-book of comparative anatomy . nals; mu, mouth; an, anus. phagus ; it is continued into the abdomen as a ganglionic ventral circular ganglionic mass of the cephalothorax is found to consistof the brain, which lies in front of the oesophagus, and gives off nervesto the lateral eyes and the ocelli, and of 7 postoral pairs of ganglia Aviththeir transverse commissures, these ganglia lying near each latter yield the nerAres for the cephalothoracic limbs. The ventralchord of the abdomen consists of 6 ganglia, the last of Avhich is thelargest. The nerves to the leaf-like feet
Text-book of comparative anatomy . nals; mu, mouth; an, anus. phagus ; it is continued into the abdomen as a ganglionic ventral circular ganglionic mass of the cephalothorax is found to consistof the brain, which lies in front of the oesophagus, and gives off nervesto the lateral eyes and the ocelli, and of 7 postoral pairs of ganglia Aviththeir transverse commissures, these ganglia lying near each latter yield the nerAres for the cephalothoracic limbs. The ventralchord of the abdomen consists of 6 ganglia, the last of Avhich is thelargest. The nerves to the leaf-like feet are given oft* by theselatter. The compound eye of Lit twins (Fig. 286) deserves special descrip-tion. The chitinous cara-pace is thickened over eachof the tAvo compound eyes;outAvardly its surface issmooth, but inwardly, bythe formation of conicalprocesses, it pushes in thesubjacent hypodermis toform toAvards the interioran equal number of papillae ;each of these chitinous conesmay be considered as alens. A completely r—CO let-. n. Km. 286.—Part of a section through the eye of Lirn-Separate retiliula probably ulus. cp, Chitinous carapace; a; papilla-like thickeningsconsisting Of 10 cells, with °* the same over each single eye; ty, hypodermis; ret, ~ retmula-; n, nerves of the single eyes. rhabdom, pigment, and nerve, corresponds Avith each of these single lenses. The retinulffi lie 420 COMPARATIVE ANATOMY CHAP. in the hypodermis. The compound eye of Limulus is thus seen to becomposed of numerous independent unilaminate single eyes crowdedtogether. Each single eye corresponds with the unilaminate eye ofcertain Myriapoda and Scorpionidce, and the whole compound eye cor-responds Avith the sum of the eyes on one side of these Arthropoda,except that the chitinous carapace in Limulus forms a thickeningcommon to all the single eyes. Enteric Canal.—From the large mouth a long oesophagus risesupward and forward, to enter a muscular masticatory- or fore-stomachplaced in the anter
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
