258 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



real work beiug to entrap minute crustaceans, worms, larvae, &c., for 

 its snpjiort, and without a good supply of wLich it is impossible to keep 

 it alive in an aquarium. 



Their form is that of a flattened ovoid sac, or, in other words, when 

 seen under a low-power microscope, they are precisely like a human 

 stomach, and tbey are attached at their hinder extremities each by a 

 very short and fine pedicle or foot-stalk in the axil of the leaves. 



Each, too, has an opening at the opposite free extremity, somewhat 

 quadrangular in outline, from either side of which i^roject two branched 

 processes, called by Mr. Darwin antennae. 



In fact, I do not suj)pose they could have received a more appropriate 

 name, because in appearance the whole bladder intimately resembles 

 an eutomostracan crustacean, the s^hort footstalk representing the tail. 



On either side of the quadrangular entrance several long bristles pro- 

 ject outwards, and these bristles, together with the branches of the 

 antennae, form a sort of hollow cone surrounding the entrance, and 

 there cannot be the slightest doubt that they act as a guide for the prey. 



The entrance is closed by a valve, which being attached above slopes 

 into the cavity of the bladder, and is attached to it on all sides except 

 at its posterior or lower margin, which is free, and forms one side of the 

 slit-like opening leading into the bladder. 



Differing materially from the color of the bladder itself, which is of 

 a brilliant green, the valve is colorless and transparent, and is extremely 

 flexible and elastic. 



Animals enter the bladders by bending inwards the posterior free 

 edge of the valve, which, from being highly elastic, shuts again imme- 

 diately. 



The edge is extremely thin and fits closely against the edge of the 

 collar, both projecting into the bladder, and it is extremely difficult, if 

 not impossible, for any animal to escape, although I have observed a long 

 ■worm do so at the expense of a part of its body ; yet, as a rule, it is a 

 case of " all who enter here lose hope." 



To show how closely the edge fits, it was found that a daphnia, which 

 had inserted its antennte into the slit, was held fast a whole day, and 

 on other occasions long narrow larvse, both dead and alive, were seen 

 wedged between the valve and the collar with their bodies half in and 

 half out the vesicle. 



When a fish is caught, the head is usually ]mshed as far into the blad- 

 der as possible till the snout touches the hinder wall. The two black 

 e^es of the fish then show out conspicuously through the wall of the 

 bladder. 



So far as is known, there is no digestive process in Utricularia 

 neither is there any sensibility to irritation. Mr. Darwin was unable 

 to detect either, his opinion being that whatever nutriment the plant 

 obtained from its prey was by absorption of the decaying matter, and 

 it would appear that the longer of the two i)airs of projections compos- 

 ing the quadrifld i)rocesses by which the vesicles are lined, which pro- 



