Anterior Segments of Earthivorm. 125 



Posteriorly to the g-izzard the dorsal vessel is seen to give off two, 

 or sometimes three, vessels in each segment on each side, which 

 pass round the intestine, in close connection with its walls, and 

 indeed invested by the glandular hepatic tissue which forms here 

 the exterior layer of the coats of the tube, to join a sub- intestinal 

 vessel. This vessel is not so closely attached to the digestive tube 

 as is the dorsal vessel, but is loosely suspended between the nerve 

 cord and the intestine. It gives off branches to the segmental 

 organs, and is connected with a third set of longitudinal vessels 

 which are in close relation with the several aspects of the nerve 

 cord, one inferiorly and two laterally, and send branches outwards 

 with the nerves. In possessing this vascular supply to the seg- 

 mental organs, and this third set of longitudinal vessels, the 

 Lumbrici differ from other Oligochaetous worms. The commis- 

 sural vessels connecting the dorsal and the sub -intestinal are 

 reduced in number to a single pair in each segment, anteriorly to 

 the crop and posteriorly to the pharynx; but they are so much 

 enlarged in size as to have been called Miearts,^ in about six 

 segments posteriorly to the pharynx. In the first six segments of 

 the body corresponding with the pharynx, both the dorsal vessel 

 and the commissural vessels are resolved into plexuses. 



Anteriorly to the crop and in the line of the outer row of setae 

 are seen the large pendulous lobes which are the vesiculae seminales, 

 increasing in size from the ninth segment, where the first of the 

 three is attached, backwards. On the left side, the posterior 

 having been displaced a little backwards from the middle vesicula 

 seminalis, the corrugated funnel-shaped opening of the posterior 

 of the two branches of the left vas deferens is seen in the interval 

 between them. Immediately exteriorly to the line of attachment 

 of the vesiculae seminales are the so-called 'capsulo-genous-* glands, 

 which appear to be due to the development in these segments of 

 the setiparous glands of the inner row of setae ; and more ex- 

 teriorly again, in the intervals between the ninth and tenth and 

 the tenth and eleventh segments, are seen the two globular recep- 

 tacula seminis in the line of the external series of locomotor setae. 

 On the walls of the oesophagus, in the segments corresponding 

 to the two posterior vesiculae seminales, may be seen the oeso- 

 phageal or ' calciferous' glands, structures said to attain a great 

 development in the Perichaetous worms. On the internal surface 



