on the valve, and after a few hours it was found fixed, half within the bladder and half projecting out, with the edge of the valve fitting closely all round, except at one angle, where a small open space was left.  It was so firmly fixed, like the above-mentioned larvae, that the bladder was torn from the branch and shaken, and yet the splinter did not fall out.  My son also placed little cubes (about 1/65 of an inch, .391 mm.) of green box-wood, which were just heavy enough to sink in water, on three valves.  These were examined after 19 hrs. 30 m., and were still lying on the valves; but after 22 hrs. 30 m. one was found enclosed.  I may here mention that I found in a bladder on a naturally growing plant a grain of sand, and in another bladder three grains; these must have fallen by some accident on the valves, and then entered like the particles of glass.

The slow bending of the valve from the weight of particles of glass and even of box-wood, though largely supported by the water, is, I suppose, analogous to the slow bending of colloid substances.  For instance, particles of glass were placed on various points of narrow strips of moistened gelatine, and these yielded and became bent with extreme slowness.  It is much more difficult to understand how gently moving a particle from one part of a valve to another causes it suddenly to open.  To ascertain whether the valves were endowed with irritability, the surfaces of several were scratched with a needle or brushed with a fine camel-hair brush, so as to imitate the crawling movement of small crustaceans, but the valve did not open.  Some bladders, before being brushed, were left for a time in water at temperatures between 80o and 130o F. (26o.6-54o.4 Cent.), as, judging from a wide- [page 408] spread analogy, this would have rendered them more sensitive to irritation, or would by itself have excited movement; but no effect was produced.  We may, therefore, conclude that animals enter merely by forcing their way through the slit-like orifice; their heads serving as a wedge.  But I am surprised that such small and weak creatures as are often captured (for instance, the nauplius of a crustacean, and a tardigrade) should be strong enough to act in this manner, seeing that it was difficult to push in one end of a bit of a hair 1/4 of an inch in length.  Nevertheless, it is certain that weak and small creatures do enter, and Mrs. Treat, of New Jersey, has been more successful than any other observer, and has often witnessed in the case of Utricularia clandestina the whole process.* She saw a tardigrade slowly walking round a bladder, as if reconnoitring; at last it crawled into the depression where the valve lies, and then easily entered.  She also witnessed the entrapment of various minute crustaceans.  Cypris “was “quite wary, but nevertheless was often caught.  “Coming to the entrance of a bladder, it would some-"times pause a moment, and then dash away; at “other times it would come close up, and even ven-"ture part of the way