SEXUAL OKGANS OF SCOLOPENDBA. 



289 



Fig. 143. 



composed of two sets of muscular fibres, of which the inner stratum is 

 disposed longitudinally, while the external one is formed of numerous 

 short, broad, transverse muscular bands, very much resembling in ap- 

 pearance the cartilaginous rings of the trachea in vertebrated animals. 

 They do not completely encircle the longitudinal ones, but pass only half- 

 way round on each side, leaving a space between those of the two sides, 

 both upon the upper and under surface. 



(746.) Prom each compartment of the heart proceed the systemic 

 arteries, which supply nearly the whole of the blood to the viscera and 

 lateral portions of each segment. The anterior pair of these systemic 

 arteries, however, instead of being distributed like the rest, form a vas- 

 cular collar, which, after surrounding the cesophageal tube (to which, and 

 to the different parts belonging to the cephalic segment, it gives off 

 numerous branches), unites beneath the oesophagus to form the great 

 supra-ganglionic vessel or aortic 

 trunk,extendingbackwards along 

 the middle line of the body, 

 immediately above the centres 

 of the nervous system (which it 

 supplies plentifully with blood), 

 as far as the terminal ganglion 

 in the last segment, giving off 

 in its course numerous arterial 

 canals, which ramify extensively 

 in the surrounding structures. 

 The return of the blood from the 

 various viscera to the dorsal ves- 

 sel is effected, as in insects, by 

 lacunar or interstitial channels, 

 as will be explained in the next 

 chapter. 



(747.) In the position and ar- 

 rangement of the sexual organs, 

 the Scolopendridee complete the 

 transition between the Anne- 

 lidans and Insects properly so 

 called ; for while in Julus we 

 have found them still occupying 

 the anterior part of the body as in 

 the former class, in Scolopendra 

 they are removed to the tail. 

 The structure of the male organs 

 (fig. 143, 2) is remarkable. The 

 testes are seven in number ; and 

 on opening the posterior segments of the animal, they are found closely 



u 



1. Female, and 2. Male generative system of 

 Scolopendra. 



