Chap. XVII.] MANNER OF CAPTURING PREY. 331 



a bladder, it would sometimes pause a moment, and then 

 dash away; at other times it would come close up, and even 

 venture part of the way into the entrance and back out as 

 if afraid. Another, more heedless, would open the door and 

 walk in; but it was no sooner in than it manifested alarm, 

 drew in its feet and antenna?, and closed its shell." Larvaj, 

 apparently of gnats, when " feeding near the entrance, are 

 pretty certain to run their heads into the net, whence there 

 is no retreat. A large larva is sometimes three or four hours 

 in being swallowed, the process bringing to mind what I 

 have witnessed when a small snake makes a large frog its 

 victim." But as the valve does not appear to be in the least 

 irritable,' the slow swallowing process must be the effect of 

 the onward movement of the larva. 



It is difficult to conjecture what can attract so many 

 creatures, animal- and vegetable-feeding crustaceans, worms, 

 tardigrades, and various larvae, to enter the bladders. Mrs. 

 Treat says that the larvae just referred to are vegetable feed- 

 ers, and seem to have a special liking for the long bristles 

 round the valve, but this taste will not account for the en- 

 trance of animal-feeding crustaceans. Perhaps small aquat- 

 ic animals habitually try to enter every small crevice, like 

 that between the valve and collar, in search of food or pro- 

 tection. It is not probable that the remarkable transparency 

 of the valve is an accidental circumstance, and the spot of 

 light thus formed may serve as a guide. The long bristles 

 round the entrance apparently serve for the same purpose. 

 I believe that this is the case, because the bladders of some 

 epiphytic and marsh species of Utricularia which live em- 

 bedded either in entangled vegetation or in mud, have no 

 bristles round the entrance, and these under such conditions 

 would be of no service as a guide. Nevertheless, with these 

 epiphytic and marsh species, two pairs of bristles project from 

 the surface of the valve, as in the aquatic species; and their 

 use probably is to prevent too large animals from trying to 

 force an entrance into the bladder, thus rupturing the orifice. 



As under favourable circumstances most of the bladders 

 succeed in securing prey, in one case as many as ten crusta- 



[Gnlded by her observations conohideg that the valve Is Ir- 

 (' Harper's Magazine.' Feb. 1870) rltable. F. D.] 

 00 the act of capture, Mrs. Treat 



