172 THE MORPHOLOGY OF THE COMMON CRAYFISH. 
In the antenna (fig. 48, C) the protopodite is two- 
jointed. The basal segment is small, and its ventral 
face presents the conical prominence on the posterior 
aspect of which is the aperture of the duct of the renal 
gland (gg). ‘The terminal segment is larger and is subdi- 
vided by deep longitudinal folds, one upon the dorsal and 
Fig, 48.— Astacus fluviatilis.—A, eye-stalk ; B, antennule; C, antenna 
of the left side (x 3). a, spine of the basal joint of the antennule ; 
e, corneal surface of the eye; exp, exopodite or squame of the 
antenna ; gg, aperture of the duct of the green gland. 
one upon the ventral face, into two moieties which are 
more or less moveable upon one another. In front and 
externally it bears the broad flat squame (exp) of the an- 
tenna, as an exopodite. Internally, the long annulated 
“‘ feeler ” which represents the endopodite, is connected 
with it by two stout basal segments. 
