324 W. BLAXLAND BENHAM. 



venous as opposed to arterial blood ; and in fact, as Professor 

 Lankester suggested to me, this is probably due to the reduced 

 condition of the hsetnoglobin in the blood. 



The vessels supplying the nephridium, as shown in the dia- 

 gram (fig. 3), are connected with the subintestinal vessel (F) 

 on the one hand, and with the dorsal vessel and subneural vessel 

 (SN) through the commissural vessel (d) on the other. 



It is a difficult matter to decide what course is taken by the 

 blood outside the large median trunks, where it flows forwards 

 in the dorsally, and backwards in the ventrally situated ves- 

 sels ; it also passes downwards from the dorsal to the sub- 

 intestinal vessel in the lateral hearts ; but what is its course in 

 the commissural vessels in the segments behind the gizzard ? 



A couple of years ago, when studying the arrangement of 

 vessels in Lumbricus, I succeeded after considerable trouble 

 in injecting the dorsal vessel in two specimens ; the blue 

 injection passed forward readily, but only in one or two seg- 

 ments did it pass into the commissural vessels. I have a note 

 that '' internal intestinal plexus and typhlosolar sinus received 

 injection,'^ but that only "in a few cases did injection appear 

 to pass on to the wall of intestine." By observation of the 

 narcotised worm it can readily be seen that blood flows into 

 the dorsal vessel from the commissural vessels, and this is 

 confirmed by the arrangement of the valves at the entrance. 



The course of the blood appears to be difi'erent in Micro- 

 ch£eta, Urochaeta, and Megascolex.^ 



I believe from the above experiments and observations (which 

 I intend to pursue further) that the blood usually passes from 

 the subneural {SN) into the dorsal vessel by way of the com- 

 missural vessels {d) ; the latter receives, amongst other branches, 

 one from the body-wall (e), another from the nephridium (/) ; 

 the blood is therefore aerated in the body-wall and deuitro- 

 genised in the nephridium before it reaches the dorsal vessel. 



The blood, in passing backwards along the subintestinal 

 trunk (F), passes outwards through the lateral (a) branches 

 to the nephridium (c), and to the body-wall (b). The former 

 » A. G. Bourne, ' Quart. Journ. Micr. Sci.,' 1891, February. 



