NEPHRIDIA AND BODY-CAVITY OF DECAPOD CRUSTACEA. 407 



probability be found in Malacostraca larvae, and he figures 

 what he takes to be this gland in a stomatopod larva (No. 2, 

 pi. iv, fig. 8). He has subsequently shown that the gland 

 exists in Anisopods and Isopods (No. 7). In a figure of a 

 Callianassa larva in the mysis stage, Claus also inserts and 

 names the shell-gland, opening on the posterior surface of 

 the second maxilla (No. 5, pi. v, fig. 42). I believe that this 

 is the only recorded instance of the gland having been recog- 

 nised in a Decapod at any stage. It occurs, however, in the 

 larvae both of Palaemonetes and of Palsemon, and at the 

 time of hatching is in a much more highly developed state 

 than the green gland. It is, in fact, at this time the functional 

 renal organ of the animal, the green gland being still without 

 a lumen, and only showing very faintly the characteristic 

 striation of the protoplasm. 



The shell-gland of Palaemonetes has the typical structure 

 of a crustacean nephridium (fig. 6, sh. gl.; figs. 7 and 8). It 

 consists of a comparatively short renal tube {tu.), with a con- 

 siderable lumen, which communicates internally with the end- 

 sac (e. s.), and opens externally at the base of the second 

 maxilla (fig. 8, b, ex. o.). Fig. 6, sh. gl., and fig. 7 represent 

 transverse sections through the gland ; whilst fig. 8, a, b, and 

 c, shows three of a series of sagittal sections, of which a is 

 more internal and c more external than b. The general form 

 of the tube may be expressed by saying that it is Y-shaped, 

 the two arms of the Y being in a horizontal plane, with the 

 end-sac attached to the internal one, whilst the leg of the Y is 

 curved in a vertical plane, the concavity looking downwards 

 and backwards. Fig. 6, sh. gl., and fig. 7 both pass through 

 the two arms of the Y, and through the point of attachment of 

 the end-sac. 



The end-sac (e. s.), which is suspended from the body-wall 

 by bands of connective tissue, has a similar structure to the 

 end-sacs of the green glands of Estheria and Mysis as 

 figured by Grobben (No. 10), and to those of the green gland 

 and shell-gland of Branchipus as figured by Claus (No. 6j. 

 It will be observed, however, that in all my figures the cavity of 



