Let us have another stroll on the moors. We pass over a small brook on our way, and of course stop on the bridge and gaze into the little rivulet. What do I see about four yards off in the shade? A number of small dark-coloured patches which I recognise at once as one of our most beautiful fresh-water algae. We will gather some from the bottom. There! the little tufts are attached to the upper sides of stones. When taken out of the water, the plant looks and feels like a mass of very dark jelly. I will float a piece out in this bottle of water. Did you ever see anything more beautiful? It consists of a number of delicate branches, each arranged in a bead-like row, and from a certain resemblance which these beaded rows bear to frog-spawn, as well as from their jelly-like consistency, this alga has received the name of _Batrachospermum_, which means "frogs' spawn." If we take a bit home and spread it out carefully on a piece of drying paper, separating the numerous beaded branches one from the other with the point of a needle, and leave it to dry gradually, we shall get a very pretty object indeed. As you may suppose, the plant is a most charming object for the microscope. "Do you think," asked Willy, "it would do in my aquarium?" I have several times tried it in an aquarium; it would live for a few days, then gradually lose colour and break to pieces. The fact is that, as Dr. Hassall says, these plants "inhabit mostly pure and running waters, being usually met with in fountains, wells, and streams, the force of which is not considerable." The frog-spawn alga, therefore, will not thrive in any but the purest water, and a gentle flow is necessary to its growth and health. "These plants are so exceedingly flexible," Dr. Hassall continues, "that they obey the slightest motion of the fluid which surrounds them, and would seem almost to be endowed with vitality; nothing can surpass the ease and grace of their movements. When removed from the water they lose all form, and appear like pieces of jelly without trace of organization. On immersion, however, the branches again quickly resume their former disposition. They adhere strongly to paper, and in drying frequently change to some other tint usually much deeper; on being moistened after long intervals they recover much of their original freshness; and it is even asserted that, after having lain in the herbarium for some years, when they are replaced in water in a suitable locality, they will vegetate as before." This last assertion I must say I do not credit. I shall never forget the delight I felt when I first made the acquaintance of this curious and graceful alga. From the eyes of how many people are its charms hidden! It is only those that look closely that would notice the little jelly-like tufts growing modestly in shaded places for the most part. This species, however, is common enough in gently flowing and shallow streams, and