ON MEGASCOLBX COERULEtlS. ?9 



ventral vessels at their anterior extremities. The existence of a 

 peripharyngeal vessel would be, of course, inimical to my theory. 

 Even Jaquet (6, p. 340, and fig. 35), who asserts its existence, 

 figures it as becoming capillary at one portion of its course. 

 I am certain that it does not exist in Megascolex ; in fact, the 

 capillaries of the most anterior branches of the dorsal and ventral 

 vessels are not connected from a functional point of view with 

 one another, but all with those of the intestino-tegumentary 

 vessels. 



It follows from what I have said that, with regard to the 

 capillary networks, the afferent vessels of the peripheral net- 

 works are in all cases branches of the dorsal and ventral vessels, 

 while their efferent vessels are branches of intestino-tegu- 

 mentary vessels, and the afferent branches of the intestinal 

 networks are branches of the intestino-tegumentary trunks, and 

 their efferent vessels are branches of either the typhlosolar, the 

 supra-intestinal, or the dorsal vessel, so that blood coming from 

 them is driven either into the hearts or into the dorsal vessel 

 at its anterior extremity, and thus in either case into peri- 

 pheral networks, so into the intestino-tegumentary system, and 

 once more into the intestinal capillaries. 



Every observation which I have made in Megascolex tends 

 to bear out this theory of the circulation. The theory has, as 

 I have implied above, this undoubted merit, that it exhibits 

 the vascular system as a perfectly metamerically segmented 

 organ, that portion of it contained in the cephalized region 

 representing, as a whole, almost exactly the portion contained 

 in any other segment of the body ; the former has undergone, 

 in fact, a synthesis, and certain additional structures, the 

 hearts, have become developed in this region. 



I may add a word or two about certain special points. 



The narrow portions which join the heart to the dorsal or 

 supra-intestinal vessels, or to both, found in so many worms, 

 possess no little interest. In the most complicated case, that 

 of a latero-intestinal heart, blood flows into the heart from 

 the dorsal and from the supra-intestinal vessel, and fills it ; the 

 muscles at the point where the heart swells then act like a 



