ON MEGASCOLEX CCERULETJS. 61 



terminates by bifurcating, and thus giving off its most anterior 

 and posterior branches, which are described under the heading 

 Ventro-tegumentary Vessels (see p. 72). 



Supra-intestinal Vessels (figs. 4 to 6).— There arenas 

 Beddard states, two of these vessels lying side by side, but 

 widely separated, on the wall of the oesophagus in segments 

 IX to XIII. The two are joined by commissural vessels in 

 segments x to xiii. In segment ix they lose themselves in the 

 intestinal capillary network, and in segment xiv they join, and 

 a very small median supra-intestinal vessel runs on into seg- 

 ment XVI, where it bifurcates and joins the dorso-intestinal 

 vessels of that segment (fig. 5). It is not continued into the 

 region of the intestine properly so called ; there is consequently 

 no typhlosolar trunk.^ 



The supra-intestinal vessels are, as usual, closely adherent 

 to the intestinal (oesophageal, &c.) walls. 



Subneural and Latero-neural Vessels are absent.^ 



Intestino-tegumeutary Vessels (figs. 4, 6 to 10, i.t.). 

 — This name was given by Perrier (9) to a pair of symmetrical 

 longitudinal vessels which are connected at either end with a 

 network of capillaries, the one network being in connection 

 with some part of the oesophageal wall (i. e. some region in 



^ In many worms the supra-intestinal vessel is said to be prolonged back- 

 wards as the typhlosolar vessel. I should not be surprised to find that the 

 typhlosolar vessel is much more frequently absent than is supposed, if not 

 altogether so. Benhara (4, p. 286) speaks of it as an "ill-defined vessel" 

 in Microcheeta rappi. Jaquet (6, p. 346) speaks of the circulation in the 

 typhlosole as being "tres difficile a poursuivre." Vejdovsky (15, p. 110) 

 seems a little doubtful about it, and I have frequently seen in sections blood 

 in that region which I should have said at once lay in the typhlosolar vessel, 

 when further examination of the series of sections has convinced me that 

 there was only a special development of the internal intestinal capillary net- 

 work, a remnant doubtless of the sinus around the intestine of many 

 Chsetopoda. 



2 Lankester (7) calls the subneural vessel the ventral vessel, but I prefer to 

 use this latter term for the subintestinal vessel, the latter being constant in 

 the Oligochseta, while the subneural vessel is absent in all the simpler and 

 many of the more complicated forms, e.g. many, if not all, Perichaetidae, Pon- 

 todrilus, and Microchseta. 



