a short skate on the surface of the water and then stopping; having measured that distance, off they go again. However, many spiders do run along on the surface of the water, and you know there is one, the great water-spider, that lives habitually in it. Some years ago I had one of these water-spiders in a glass vessel of water, and saw it spin its curious dome-shaped web which it attached to the sides of the glass and some weeds. These domes are formed of closely woven white silk, in the form of a diving bell or half a pigeon's egg, as De Geer has said, with the opening below. It looks like a half-ball of silver; this appearance is due to a quantity of air. It is, in fact, a huge air-bubble surrounded by a covering of white silk, and, as you may suppose, a very interesting and pretty object. Within this silver dome the spider places her eggs, perhaps a hundred or more in number, which are enveloped in a cocoon, this being attached to the inner side of the dome. "But how," said Jack, "is the bubble formed? Where does the air come from?" You have asked a very interesting question, and one which can be answered; for the question was set at rest by Mr. Bell, an excellent observer and well-known naturalist, about twelve years ago, if I remember rightly. He found that the old spider actually took the air down with her from the surface of the water, and deposited it in her domed house. I shall now quote Mr. Bell's words: "The manner in which the animal possesses itself of the bubble of air is very curious, and, as far as I know, has never been exactly described. It ascends to the surface slowly, assisted by a thread attached to a leaf or other support below and to the surface of the water. As soon as it comes near the surface it turns with the extremity of the abdomen upwards, and exposes a portion of the body to the air for an instant, then with a jerk it snatches, as it were, a bubble of air, which is not only attached to the hairs which cover the abdomen, but is held on by the two hinder legs, which are crossed at an acute angle near their extremity; this crossing of the legs taking place at the instant the bubble is seized. The little creature then descends more rapidly and regains its cell, always by the same route, turns the abdomen within it, and disengages the bubble." Spiders have strong jaws; at the bottom of each hooked jaw there is a small sac which contains a poisonous fluid; this fluid is conveyed by a narrow channel from the sac along the jaw, and is pressed out at an opening or slit at the tip of the fang into the wound inflicted on its victim. The feet of spiders are generally terminated by two or more claws furnished with teeth; by means of these combs the animal is enabled to manage the threads of its web with great dexterity and efficiency. [Illustration: SPIDER'S FANG, MAGNIFIED.] [Illustration: SPIDER'S FOOT, MAGNIFIED.] [Illustration] WALK IX. JULY.