IS THE VALVE OF UTRICULAEIA SENSITIVE? 157 



as to imitate the crawling movements of small crusta- 

 ceans; but the valve did not open." And farther on 

 he adds : " On three occasions minute particles of blue 

 glass (so as to be easily distinguished) were placed on 

 valves while under water. On trying gently to move 

 them with a needle they disappeared so suddenly that, 

 not seeing what had happened,! thought that I had 

 flirted them off; but on examining the bladders they 

 were found safely enclosed. The same thing occurred 

 to my son, who placed little cubes of green boxwood 

 (about one -sixtieth of an inch) on some valves; and 

 thrice in the act of placing them on, or while gently 

 moving them to another spot, the valve suddenly opened 

 and they were engulfed." The same thing occurred to 

 me several times when I was gently moving minute 

 particles of various substances on the edge of the valve 

 — it suddenly opened and took them in ; which helped 

 to confirm me in the belief that the valve was sensitive, 

 and that the sensitiveness was of a special nature. But 

 not upon these experiments did I wholly base my infer- 

 ence ; it was based more upon observations made upon 

 the growing plant and the living larvae. By putting a 

 spray of the plant and water under a low power of the 

 microscope I could thus bring several utricles into the 

 field, with numerous mosquito larvae. If the tail of 

 one of these larvae happened to come in contact with 

 the valve, the valve was almost sure to open and en- 

 gulf the larva, often leaving its head sticking out, as is 

 seen in Fig. 12. I have a large number of these utri- 



