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. — Astac7(s fluviatilis. — A, eye-stalk ; B, antennule ; C, antenna 

 of the left side ( x 3). a, spine of the basal joint of the antennule ; 

 c, corneal surface of the eye ; e.vjy, 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. 



