458 ALFRED GTEBS BOURNE. 



arise ; upon each side these surround, at their origin, the nerve 

 branches which arise from the ganglia. They then pass in a 

 dorsal direction, and, giving off branches, run towards the 

 dorsal sinus and open into it ; anterior branches of the same 

 trunks may do likewise (fig. 8, d. v. s.). 



In the middle region of the body these dorso-ventral sinuses 

 form spherical dilations a little beyond the point at which the 

 nerve branch leaves the sinus (fig. 8 and woodcut fig. 2, n. 

 f.) ; it is in these dilatations that the nephridial funnels are 

 lodged. Beyond this point, in the testicular region, the sinus 

 divides into two main branches. One runs at once towards the 

 dorsal sinus, the other, passing in an anterior direction, forms 

 a dilatation, which almost entirely surrounds the testis (fig. 

 63, j». ^. s., woodcut, fig. 2), a circumtesticular sinus; it then 

 passes to the dorsal vessel. 



The ventral sinus encloses, in addition to the organs men- 

 tioned above, the ovaries and the greater part of the copulatory 

 apparatus (see woodcut, fig. 2, v. s.). 



Here and there the dorsal sinus has developed in its wall a 

 muscular band, consisting of some four or five circularly 

 arranged fibres (fig. 45, m.). 



Dorsal Vessel. — The dorsal vessel, as Leydig pointed out, 

 possesses a series of valves similar to those in Clepsine. I have 

 not seen any branches arising from it. At either end it commu- 

 nicates with the ventral and, I think, lateral vessels. I am not 

 quite certain about its communication with the lateral vessels 

 anteriorly. The blood always passes from behind forwards. 



Ventral Vessel. — This does not give rise to any branches, 

 but communicates anteriorly and posteriorly, as above described, 

 with the dorsal vessel. 



Lateral Longitudinal Vessels. — Communicating cer- 

 tainly at the posterior extremity, with the dorsal and ventral 

 vessels, these run forwards without any branches to the body ; 

 anteriorly they anastomose with one another. 



Vaillant describes a connection between the lateral vessels 

 and his dorsal vessel in the somite with the first pair of testes; 

 this he demonstrated by injection. I cannot discuss the mean- 



