124 



Mr. A. Sedgwick. 



[Dec. 8. 



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

 the kidney has been seen and described by von Jehring, 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 



A diagrammatic representation of a transverse section through Chiton discrepans 

 at the level of the renal orifices (r.o., fig. 1). Dorsally is the pericardial cavity 

 with the heart, separated by the pericardial floor from the general body cavity (b.c), 

 containing the viscera. Tentrally is the posterior apparently median unpaired part 

 of the kidney (Tc.t. and Jc.c) seen by von Jehring. A little in front of this section, 

 the kidney tubules take up a distinctly lateral position. 



D ; p.ff. ; b.r. ; Jc.t. ; r.o. as in fig. 1. 



A, auricle ; T, ventricle ; b.v., branchial vein; h. a., branchial artery; p.c, peri- 

 cardial cavity; ?./?., lateral nerve (pallia!) ; jo.n., pedal nerve; F, foot ; A.C., ali- 

 mentary canal ; g.g., generative gland; b.c, body cavity; Jc.c see Tc.t. ; jp.k.d., part 

 of kidney duct which in fig. 1 is hidden from view by D. 



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, h.d.), which 

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

 glandular caeca, lying at the side of the body cavity (fig. 1, h.tJ). These 

 branching glandular caeca constitute the gland described by Midden- 

 dorff. Their structure precisely resembles that of the first described 



