516 



MTRIAPODA. 



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 impaired 

 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 (ScMtigera) 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 oesophagus 

 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 (tig. 

 420). It is divided into a great 

 number of chambers, which cor- 



1 



,V i 



FIG. 420. Head and anterior segments 

 of Scolopendra (after Newport). 6. 

 brain ; 0, eyes ; A, antenna; ; Ef, max- 

 illiped (poison-claw) ; C, heart ; M, 

 alary muscles of the heart; A r, arteries. 



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 oft'. 



All Myriapods breathe by means of tracheae. These, as in Insects, 

 receive the air from the exterior through paired slits, which are 

 found in almost ever}' segment (sometimes beneath the basal joints 



