126 On certain Points in the Anatomy of Chiton. [Dec. 8, 



The cells of the glandular caeca seem to have the structure usually 

 seen in molluscan renal organs, and have been correctly described by 

 von Jehring. 



To sum up, the kidney of Chiton consists of — 



(1.) A duct opening to the exterior in the pallial groove behind the 

 generative opening, and internally into the pericardium. 



(2.) Glandular caeca opening into this duct. 



The duct may be described as consisting of three parts : — 



(1.) The part into which the glandular cseca of the kidney open. 

 This part is open behind where it opens to the exterior (fig. 1, D). 

 In front it bends round (fig. 1, T), and runs backwards to about 

 the level of the 5th shell-plate, where it changes its character, and is 

 continuous with (2) a duct (fig. 1, 0) containing brown colouring 

 matter in the columnar cells lining it, and receiving no glandular caeca. 

 This part extends back to the level of the last gill, where it turns out- 

 wards, and becomes continuous with (3) a part running forward for a 

 short distance close to the lateral nerve, and lined by large ciliated 

 columnar cells. This part opens in front at the level of the penulti- 

 mate gill into the pericardium (fig. l,p.o.). I expected to find the 

 communication between the two parts of the renal duct behind in the 

 region of the bladder, and for some time I was puzzled at not finding 

 it. On mentioning the arrangement of parts to Mr. Balfour, he 

 suggested that the communication might possibly be found in front, 

 reasoning from the analogy of the structure of the kidney in other 

 Mollusca. On examining the anterior part of the gland more care- 

 fully, I at once found that his suggestion was correct, the two parts of 

 the gland communicating as I have described. I have no observations 

 to add to those of previous observers, on the general arrangement of 

 the nervous system. I may mention that the lateral and pedal nerves 

 have a coating of ganglion cells, and a central core of fibres. 



The animals are dioecious. The generative gland is unpaired and 

 dorsal. The generative ducts are paired, and are attached to the 

 hinder border of the gland, and open in Chiton discrepans into the 

 pallial groove between the 13th and 14th gill, in a line with the open- 

 ing of the renal duct. The duct passes dorsal to the anterior end of 

 the dilated part of the renal duct (fig. 1, g.d.) ; and then curls round 

 the outer border of the lateral nerve-cord to its opening, presenting in 

 this respect precisely the same relation as does the renal duct. The 

 male duct has a short direct course to its opening (fig. 1) ; while the 

 female duct is much coiled. 



Another species, Chiton cancellatus, which I have examined, presents 

 essentially the same arrangement of its renal organ and generative 

 ducts as that just described for Chiton discrepans. 



Dall* states that in some species of Chiton, the generative products 

 # " Proceedings of the United States' National Museum," vol. i. 



