Haddon — On Generative and Urinary Ducts iu Chitons. 231 



pericardial opening is lined with large columnar cells, wMcli line 

 also the pericardial opening. 



Haller (11) refers to the great difficulty in the study of this 

 organ on account of its colour and delicacy. He finds that in the 

 two species he examined [Ch. siculus and C/i. caj'etanus), the sulphur- 

 yellow- coloured kidneys are paired acinose glands (fig. 3).^ " We 

 find on each side a wider portion, 

 which we will call the kidney- 

 body (' Nierenkorper'), and which 

 is in reality nothing more than a 

 wide tube into which the more 

 or less compound flaps open se- 

 parately. It extends from the 

 hinder end of the first ' shell- 

 scale' to about the middle of 

 the last; the flaps opening into 

 the kidney-body throughout its 

 length." These flaps may be di- 

 vided into two groups — the longer 

 and shorter. The latter densely 

 beset the anterior portion of the 

 kidney-body on all sides ; in the 

 hinder region, however, the upper 

 surface is nearly free from them. 

 The larger flaps, which are very 

 long, are only slightly ramified ; 

 they are grouped separately at 

 fairly constant points, and only 

 open mesially, and on the under 

 side of the kidney-body, except 

 at the hinder end. These long 

 flaps are arranged in eight brush- 

 like groups, corresponding to the 

 hinder border of each shell. The 

 flaps of one side often overlap 



Fig. 3. 



Dissection of the renal organs (nephridia 

 of Chiton siculus, after Haller (ii). F, foot ; 

 L, edge of the mantle not removed in the 

 front part of the specimen ; s.o., oesophagus ; 

 af, anus ; gg, genital duct ; go, external 

 opening of the same ; eg, stem of the nephri- 

 dium leading to no, its external aperture ; 

 nk, reflected portion of the nephridial stem ; 

 ng, fine caeca of the nephridium, which are 

 seen ramifying transversely over the whole 

 inner surface of the pedal muscular mass. 



^ Fig. 3 is reproduced, by permission of the publishers, from Fig. 15 of Professor 

 E. Ray Lankester's article " Mollusca," in the last edition of the Encyclopadia 

 JSritannica. 



