100 ADAM SEDGWICK. 



tions, SO far as they went, were perfectly correct. The 

 paired lateral-branched glaud described by the latter observer 

 is part of the kidney. 



The kidney of Chiton is a paired glaud with paired open- 

 ings into the pallial groove and into the pericardium, and is 

 constructed on the type always found in moUuscan renal 

 organs (fig, 1). It opens in the species I have chiefly 

 examined [Chiton discrepans) into the pallial groove (fig. 

 1, r.o.) internal to, but on a level with the last gill (16). 

 The duct runs from the opening round the outside border of 

 the pallial nerve (fig. 2, r.o.), and then passes inwards to 

 open into a bladder-like structure placed in the body cavity 

 (tig. ] , D, and fig. 2, D). This bladder-like structure lies 

 close to the body wall immediately beneath the pericardium 

 (fig. 2, P'C), and it does not seem to extend backwards 

 beyond the last gill. 



On a closer examination by means of sections, it is seen 

 to be beset by a number of branched glandular cseca, lying 

 in the hinder part of the body cavity (fig. 2, k.t.), which 

 open into it, and into a backward prolongation from it 

 (fig. 1, h.k.). These branched glandular cseca on opening 

 the body cavity are seen as a mass of tubes apparently inter- 

 lacing with those of tne opposite side, and lying ventral to 

 the rectum on the floor of the body cavity (fig. 2, k.t.). This 

 portion of the kidney has been seen and described by von 

 Jhering, but instead of constituting the whole of the kidney 

 and opening to the exterior by a median pore, it is only the 

 posterior part, and opens on each side into the bladder-like 

 structure which opens to the exterior in the position 

 described above. I have many series of sections through 

 this hinder part of the kidney of Chiton, which prove most 

 conclusively that these hinder ventrally-placed tubules do 

 open in the way I have stated. 



On examining the anterior end of the bladder-like structure 

 it is found that it is continued forwards as a duct (fig. 1, k.d.), 

 which receives, all along its course, the ducts of bunches of 

 branching glandular cseca, lying at the side of the body 

 cavity (fig. 1, k.t.). These branching glandular cseca con- 

 stitute the gland described by MiddendorS". Their structure 

 precisely resembles that of the first described posterior 

 tubules, which open into the dilated part of the duct and its 

 backward prolongation. The duct can be traced forward to 

 about the level of the fourth shell-plate (fig. 1, T), at which 

 point it turns sharply round and runs back parallel with the 

 first part of its course. A considerable part of the gland 

 lies in front of this turning point of the duct ; the secretion 



