538 



ZOOLOGY 



SECT. 



methods, the total number of gills, viz., eighteen complete gills 

 with two vestiges and seven epipodites. 



The excretory organs differ both in position and in form 



from those of 

 Apus. There are 

 no shell-g lands, 

 but at the base 

 of each antenna is 

 an organ of a 

 greenish colour, 

 the antennary or 

 green gland, by 

 which the function 

 of renal excretion 

 is performed. The 

 gland (Fig. 445) is 

 cushion - shaped, 

 and consists o f 

 three parts (1) a 

 central saccule (s.) 

 of a yellowish 

 colour, occupying 

 the mid - dorsal 

 region, and con- 

 sisting of a sac 

 divided into 

 numerous c o m - 

 partments by par- 

 titions, and com- 

 municating with 

 (2) the outer or 

 cortical portion 



/ ~> \ n f Q rrrppn 

 . . \ C ' P')> " 



s. saccule ; u\ p. white por- COIOUT Consisting 



FIG. 445. Diagram of kidney of Astacus fluviatilis. I, mi- 

 ravelled; II, the parts in their natural relations. W. bladder ; 



c. p. cortical portion ; d. duct; 

 tion. (After Marchal.) 



