Cuav. XVII. MANNER OF CAPTURING PREY. 405 
grown bladders contained prey; in a second lot, re- 
ceived in the beginning of August, most of the 
bladders were empty, but plants had been selected 
which had grown in unusually pure water. In the 
first lot, my son examined seventeen bladders, in- 
cluding prey of some kind, and eight of these con- 
tained entomostracan crustaceans, three larve of in- 
sects, one being still alive, and six remnants of 
animals so much decayed that their nature could not 
be distinguished. I picked out five bladders which 
seemed very full, and found in them four, five, eight, 
and ten crustaceans, and in the fifth a single much 
elongated larva. In five other bladders, selected from 
containing remains, but not appearing very full, there 
were one, two, four, two, and five crustaceans. A plant 
of Utricularia vulgaris, which had been kept in almost 
pure water, was placed by Cohn one evening into water 
swarming with crustaceans, and by the next morning 
most of the bladders contained these animals entrapped 
and swimming round and round their prisons. They 
remained alive for several days; but at last perished, 
asphyxiated, as I suppose, by the oxygen in the water 
having been all consumed. Freshwater worms were 
also found by Cohn in some bladders. In all cases 
the bladders with decayed remains swarmed with 
living Alge of many kinds, Infusoria, and other low 
organisms, which evidently lived as intruders. 
Animals enter the bladders by bending inwards the 
posterior free edge of the valve, which from being 
highly elastic shuts again instantly. As the edge is 
extremely thin, and fits closely against the edge of the 
collar, both projecting into the bladder (see section, 
fig. 20), it would evidently be very difficult for any 
animal to get out when once imprisoned, and apparently 
they never do escape. To show how closely the edge 
