494 Miscellaneous. 



chial aimstomosis ; this latter portion, which is at first wide, 

 diminishes gradually to the commencement of the stomach ; beyond 

 this point it floats in the general cavity, but remains parallel to the 

 oesophagus, to which it is attached by a few branches; finally it 

 attaches itself to the pharynx, where it divides into numerous 

 branches, the two principal ones forming a fork. 



The ventral vessel has numerous roots at the ventral surface of 

 the pharynx and the anterior setas ; it travels parallel to the ner- 

 vous cord, to which it sends several branches, and emits numerous 

 branches to the segmental organs, which will be mentioned further 

 on ; then, towards the middle of the body, it gives origin (1) to a 

 vessel which follows forward the posterior intestine, (2) to two 

 other trunks, the most voluminous of which soon divides into three. 

 Thus are formed the four sexual vessels, upon which the generative 

 organs originate. Three of them run along different portions of the 

 stomach, the fourth along the recurrent intestine ; they give origin 

 to very numerous branches, which divide repeatedly and generally 

 dichotomously, and finally open into a sinus lodged beneath the 

 muscular layer of the intestine and against the vibratile furrow. 

 The latter, in the stomachal region, is diametrically opposite to the 

 dorsal vessel, which communicates with this longitudinal sinus by a 

 very complex system of capillary canals, destitute of proper mem- 

 brane, and placed between the muscular layer and the epithelium. 

 The whole intestine is thus furnished with a very rich system of 

 blood-sinuses, communicating with both the dorsal vessel and the 

 ventral vessel along the pharynx, oesophagus, and stomach, but 

 having direct connexion with the ventral vessel alone through all 

 the rest of the intestine ; there are, however, vascular anastomoses 

 between the different intestinal regions. 



Further back the ventral vessel emits numerous symmetrical 

 branches, which run to the integuments, the posterior setse, and the 

 terminal intestine ; some of them terminate posteriorly at regular 

 racemes of ampullae or pyriform bodies with thin walls placed be- 

 tween the shield and the rectum, and evidently forming a reservoir 

 for the blood when that fluid is driven backward by the invagina- 

 tion and contraction of the anterior region of the body. I have 

 been unable to detect any communication between these racemes 

 and the branchia3. The circulation seems to me to be due princi- 

 pally to the general movements of the body. 



The generative organs are of the same form in the two sexes. 

 The external appendages are followed by two oviducts or sperm- 

 ducts, which run backward towards the median line, where they 

 unite and at the same time adhere to the ventral vessel ; each of them 

 is accompanied by a sanguiferous branch, which is given off by this 

 same ventral vessel, and which only quits them at the skin ; from 

 their point of convergence start the four lobes of the ovary or testis. 

 These lobes are slowly formed along the four sexual vessels already 

 mentioned ; they possess each a proper wall, which is directly con- 

 tinuous with that of the oviducts, and in which the corresponding 

 sexual vessel is enclosed. The ova originate upon the wall of this 



