284 W. F. R. WELDON. 



pendently at the conclusion that the blood system of the 

 Decapod Crustacea is everywhere closed ; but I am not aware 

 that either of these observers has paid special attention to the 

 blood-supply of the renal organs. Nevertheless, the positive 

 testimony of two such accomplished anatomists makes me 

 hesitate to lay undue stress upon my own failure to demon- 

 strate an epithelial lining to the particular spaces under con- 

 sideration. 



The epithelium of the end-sac, like that of the rest of the 

 excretory system, is everywhere one cell thick. The indi- 

 vidual cells stain more deeply than do those of the bladder 

 and renal tubule ; their protoplasm is crowded with granules, 

 which are, however, not arranged in regular rows, so that the 

 cells do not exhibit a longitudinal striation. The nuclei stain 

 very deeply, and exhibit, in specimens preserved in corrosive 

 sublimate, one or two large nucleoli, with no recognisable 

 trace of a chromatin reticulum, The inner extremities of 

 these cells are much vacuolated, and are very irregular ; the 

 vacuoles frequently containing spherical concretions of a homo- 

 geneous material, which stains slightly with hsematoxylin, 

 less readily with borax carmine. The cavity of the end-sac is 

 generally found to contain a greater or less quantity of granular 

 clotted material, which appears in sections as a deeply staining, 

 finely granular reticulum. 



In Pandalus (annulicornis and brevirostris) a further 

 deviation from the tubular type of uephridium occurs, the 

 renal tubule being in the adult condition entirely absent, 

 while the whole body of the '^ green gland " is built up of the 

 curiously modified end-sac and the associated portion of the 

 wall of the bladder. 



I have not followed the early phenomena of the development 

 of the kidney ; but in the late '^ Mysis " stage the relations of 

 kidney and bladder present a striking resemblance to those 

 which are permanent throughout life in Virbius. The 

 appearance presented at this stage in horizontal longitudinal 

 section is shown in PI. XXI, fig. 5. 



The bladder is large compared with the size of the renal 



