One of the most common little creatures that was caught in this trap, was the Tardigrada, or water bear. He looks like a tiny cub, but unlike his great namesake, he has eight legs, and he frequently slips out of his old skin and comes out in a new suit.

I often find them crawling in a forest of these plants, peering out of a thick jungle—now ascending a branch and out on a limb, holding fast with their long claws, and apparently looking around to see what they can find.

Now one seems to be attracted to this elegant glassy cluster of Utricularia. At all events he is soon pushing his head among the delicate stems, then stops a moment, standing perfectly still as if listening. Perhaps he hears the groans of his dying comrades, but all unheeding the warning, he steps forward, touches the fatal spring, when in he goes to perish with his comrades.

FIG. 3. CHIRONOMUS LARVA:
BACK VIEW WITH FEET DRAWN
IN AND JAWS CLOSED; SIDE VIEW
WITH FEET EXTENDED
AND JAWS CLOSED.

Young microscopists may like to know that the Utricularia can be preserved in the house a long time by putting the stems or sprays in an open, shallow dish of water where they will grow readily. I have kept the plants months together in a large glass dish where they looked charmingly beautiful and were the admiration of all who saw them. It is very interesting to watch their growth. The ends of the growing sprays unroll like ferns, and with a magnifying glass you can see the development of the little bladders, and you may make discoveries—who knows? I know that for a long time it was a mystery to me how the bladders captured and imprisoned the little animals. Every day I saw they were entrapped and never escaped, and I studied and pondered over the matter a long time, and was so interested and determined to learn the secret that I spent night after night looking through the microscope, watching the strange, unwary creatures fall into the trap.

At last I concluded to adopt the following plan: I took sprays of the plants that I had grown in clear water that contained no animalcules, so that all the bladders were empty and quite transparent. In another dish I had put a great many masses of mosquito eggs. Mosquito eggs are found floating on almost any standing water, in dark, compact masses. In warm weather they hatch in a few hours. So you can understand how quickly I could swarm a small vessel of water with the mosquito larvæ by introducing the eggs where I wished them to hatch. When they were hatched I put some of the water in which was a large number of the tiny creatures into the live box with a spray of the plant containing empty bladders. I placed the box under the microscope and closely watched the manner of capture. I became certain that in almost every instance the larvæ were caught tail first. The tail is brush-like, and when it swept over the door or valve that leads into the bladder, I saw that the door would immediately fly open and always draw the larva in. I soon became satisfied that the valve was very sensitive when touched at the right point, but to this day I cannot tell what the power is that so quickly draws the creatures within. I earnestly hope that some young microscopists will yet be able to ferret out the cause of this singular power.

Those who have read Mr. Darwin's very interesting book on Insectivorous Plants, will have noticed that he says the valve of Utricularia is not in the least sensitive, and that the little creatures force their way into the bladders—their heads acting like a wedge. But this is not the case, as Mr. Darwin himself was convinced some years before his death. In his usual kind, gracious manner he admitted that he was wrong, and gracefully says the valve must be sensitive, although he could never excite any movement. In a letter to me bearing date June 1st, 1875, he says:

"I have read your article (in Harpers Magazine) with the greatest interest. It certainly appears from your excellent observations that the valve is sensitive.... I cannot understand why I could never with all my pains excite any movement. It is pretty clear I am quite wrong about the head acting like a wedge. The indraught of the living larva is astonishing."