. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 516 MYRIAPODA. Insects. The nervous system is distinguished by the great elongation of the ventral ganglionic cord, which runs along the whole length of the body and is swollen in each segment to form a ganglion. According to Newport, there is a system of paired and unpaired visceral nerves, like those of Insects. Eyes are only rarely wanting, and are usually present as ocelli which are sometimes closely packed together, or rarely (Scutigera) as peculiarly-formed facetted eyes. The alimenta
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 516 MYRIAPODA. Insects. The nervous system is distinguished by the great elongation of the ventral ganglionic cord, which runs along the whole length of the body and is swollen in each segment to form a ganglion. According to Newport, there is a system of paired and unpaired visceral nerves, like those of Insects. Eyes are only rarely wanting, and are usually present as ocelli which are sometimes closely packed together, or rarely (Scutigera) as peculiarly-formed facetted eyes. The alimentary canal, with rare exceptions (Glomeris), takes a straight course through the entire length of the body, and opens by the anus in the last segment. The following parts can be distin- guished :—a narrow (.esophagus beginning with the buccal cavity and, as in Insects, receiving the contents of two to six tubular salivary glands; a wide, very long mesenteron, the surface of which is closely beset with short hepatic tubes projecting into the body cavity; a hind gut, which receives two or four Mal- pighian tubules, the latter being coiled round the intestine; and finally a short and wide rectum. The central organ of the cir- culation is a long pulsating dor- sal vessel, which extends through all the segments of the body (fig. 420). It is divided into a great number of chambers, which cor- respond to the segmentation and, in Scolopendra, are attached to the dorsal wall by alary muscles to the right and left (fig. 420, M). The blood passes from the body cavity through lateral paired slits into the chambers of the heart, and is thence driven, partly through paired lateral arteries and partly through an anterior cephalic aorta which divides into three branches, to the organs of the body cavity, from which a blood sinus, embracing the ventral ganglionic chain, is separated off. All Myriapods breathe by means of tracheae. These, as in Insects, receive the air from the exterior through
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