Cnar. XVII STRUCTURE OF THE BLADDER. 399 
the outside, six or seven long, pointed, multicellular 
bristles. These prolongations of the bladder may be 
conveniently called the antennex, for the whole bladder 
(see fig. 17) curiously resembles an entomostracan crus- 
tacean, the short footstalk representing the tail. In 
fig. 18,,the near antenna alone is shown. Beneath 
the two antennz the end of the bladder is slightly 
truncated, and here is situated the most important 
part of the whole structure, namely the entrance and 
valve. On each side of the entrance from three to 
rarely seven long, multicellular bristles project out- 
Fig. 19. 
(Utricularva neglecta.) 
Valve of bladder; greatly enlarged. 
wards; but only those (four in number) on the near 
side are shown in the drawing. These bristles, to- 
gether with those borne by the antennae, form a sort 
of hollow cone surrounding the entrance. 
The valve slopes into the cavity of the bladder, or 
upwards in fig. 18. It is attached on all sides to 
the bladder, excepting by its posterior margin, or the 
lower one in fig. 19, which is free, and forms one side 
ot the slit-like orifice leading into the bladder. This 
margin is sharp, thin, and smooth, and rests on the 
edge of a rim or collar, which dips deeply into the 
