830 UTIilCULARIA NEGLECTA. [Chap. XVII. 



but after 22 hre. 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 blade 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 parti- 

 cles 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 gela- 

 tine, and these yielded and became bent with extreme slow- 

 ness. It is much more diflScult 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 crus- 

 taceans, but the valve did not open. Some bladders, before 

 being brushed, were left for a time in water at temperatures 

 between 80 and 130 F. (26.6 54''.4 Cent.), as, judging 

 from a widespread 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 surj^rised that such small and weak creatures as 

 are often captured (for instance, the nauplius of a crusta- 

 cean, 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 hair i of an inch in length. Nevertheless, it is 

 certain that weak and small creatures do enter, and Mrs. 

 Treat, of New Jerey, has been more successful than any 

 other observer, and has often witnessed in the case of Utricu- 

 laria 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 vari- 

 ous minute crustaceans. Cypris "was quite wary, but 

 nevertheless, was often caught. Coming to the entrance of 



' Now York Tribune,* reprinted In the ' Gardener's Chronicle,' 

 187S, p. 303. 



