NEPHRIDIA AND BODY-CAVITY OF DECAPOD CRUSTACEA. 403 



Nephridia and Body-cavity of some Decapod 

 Crustacea. 



By 



Edg:ar J. Allen, B.Sc, 



University College, London. 



With Plates XXXVI, XXXVII, & XXXVIII. 



The following paper contains the results of researches 

 carried on at the Plymouth Laboratory of the Marine Bio- 

 logical Association^ where^ by appointment of the British 

 Association Committee, I occupied a table for six weeks 

 during the summer of last year (1892), my stay being pro- 

 longed for an additional month through the kindness of Mr. 

 Robert Bayly, one of the Governors of the Association, who 

 furnished me with an additional nomination. 



The observations were made chiefly upon larvse of Palse- 

 monetes varians, but they were subsequently extended to 

 the adult of this form, as well as to larvse and adults of 

 allied species, the latter part of the work having been done 

 in Professor Weldon's laboratory at University College, 

 London. 



Palsemonetes varians is found in the brackish waters of 

 certain ditches and pools near the estuary of the Plym, which 

 are subject to the influence of the tides. 



The larvae were at first obtained by keeping gravid females, 

 whose eggs were in an advanced stage of development, in 

 separate vessels in a mixture of one part of sea water to two 

 of fresh (this mixture having about the same density as the 

 water in which the animals were captured). They were after- 



