434 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



striated appearance noted by Wei don and Allen. In some 

 cases these striations are carried through to the inner 

 region of the cell, but generally the protoplasm is divided 

 into a deeply-stained outer portion, which exhibits the 

 striations mentioned above, and a more lightly stained 

 inner portion in which the strands of protoplasm are few 

 in number, thus causing the vacuolated appearance. The 

 nucleus of the bladder epithelial cells has a diameter of 

 6/x, and is situated near the centre of the cells. 



(3) The Ureter (Text fig. 11, 12, A, Ur.) is a 

 spacious sac situated on the inner side of the antennary 

 gland, partly in front of and partly below the gland. The 

 connection with the main vesicle is a narrow opening 

 immediately in front of the anterior and inner corner of 

 the gland. The ureter passes downwards, and opens to 

 the exterior on the ventral surface of the proximal portion 

 of the second antenna. It is lined with epithelial cells, 

 which are distinctly larger than those of the bladder and 

 take the stain more distinctly. 



The relation of the parts in the neighbourhood of the 



external orifice is of interest. The proximal region of the 



ventral side of the second antenna is occupied by a small, 



irregularly-shaped plate — the operculum (PI. II, fig. 5, 



op.), which is freely movable. The movement is possible 



because of its connection, by means of a flexible 



membrane, with the surrounding hard parts. The 



membrane forms a pocket-like invagination around the 



operculum, and is deepest on the inner and posterior side, 



so that the movement is greatest on this side when the 



operculum is raised. When the operculum is elevated it 



is seen that the membrane is perforated by a distinct 



orifice on the inner and posterior side. This is the 



excretory orifice. Hence Marchal* termed the membrane 



* Marchal. " Appareil excreteur des Crustaces Decapodes." 

 Arch. Zool. exp. et gen., T. X (Ser. 2), 1892. 



