228 Scientific Proceedings, B,oyal Dublin Society, 



Yon Jhering (6) assumes that Schifi has demolished Midden- 

 dorfE's account, and asserts that " a kidney was unknown in Chiton 

 until now." He thus defines the newly-discovered (!) organ : " The 

 kidney is a tree-like ramified gland, lined with a ciliated epithelium, 

 lying upon the floor of the body- cavity ; it possesses an unpaired 

 median efferent duct, which opens below the anus." The form dis- 

 sected was Ch. fascicularis. Mr. W. H. Dall informs me that, in a 

 letter to him, Yon Jhering writes that the posterior median opening 

 of the kidney was an error of observation on his part ; and Hu- 

 brecht (10) states that " Dr. Brock, of Grottingen, kindly writes to 

 tell me that Yon Jhering has lately withdrawn this viewj as repos- 

 ing on an erroneous observation, and has been convinced of the 

 presence of lateral renal openings (prior to Sedgwick's exhaustive 

 researches)." Dall (7) " did not detect the renal organ in some cases, 

 and failed to find any excretory opening." He goes on to say, " It 

 is probable that this exists, but the contraction of the tissues of my 

 specimens by alcohol may have obliterated it." 



Sedgwick (8), in a preliminary Paper, ^ entirely and successfully 

 disproves Yon Jhering's statements, and found that " MiddendorfE's 

 observations, as far as they went, were perfectly correct." The spe- 

 cies he examined were Ch. cUscrepans and Ch. canceUatus ; the former 

 species being so closely allied to Ch. fasciculatus that it practically 

 amounts to re-examination of Yon Jhering's species. The kidney is 

 a paired dendritic gland (figs. 1 and 2),^ with an external opening 

 into the pallial groove, and an internal pericardial orifice ; it lies on 

 the side of the floor of the body cavity. Each gland consists of a 

 longitudinal duct, beset with branched glandular cseca ; about the 

 level of the last six gills this duct is swollen into a " bladder-like 

 structure," which, at its posterior end, sends out a small tube, and 

 at right angles to itself, which opens to the exterior in the pallial 

 row, and the level of the last (16th) gill. About the level of the 

 fourth shell- plate there is a second tube, which turns sharply round, 

 and runs back more or less parallel with, but above and internal to, 

 the former. It is at first also furnished with glandular cseca, but 



^ I understand that he is not intending, for the present at all events, to continue 

 his investigations. 



■^ I am enabled through the kindness of my friend Mr. Sedgwick, and by the per- 

 mission of the Eoyal Society, to introduce Mr. Sedgwick's original diagrams (Figs. 1 

 and 2) in illustration of his views. 



