Late spring and autumn are the best seasons to hunt the ponds for our next object, which rejoices in the name _Chlamydomonas Angulosa_, a good example of the extraordinary fact that some of the smallest animals and plants have the longest names. This little plant is interesting in itself and doubly so, because it was for long thought to be an animal; it is wonderfully animal-like in its movements. _Chlamydomonas_ is very minute, so we must use our highest magnification when we examine it. It is an oval, one-celled plant enclosed in a clear membrane. The green colouring matter is arranged in the form of a cup, within the hollow of which is a mass of granular living substance. At the forward end of the plant, there is a clear space and near the tip a brownish dot, known as the eye spot; which, though incapable of seeing as we understand it, is sensitive to light, as shown by the fact that the little plant will swim towards moderately intense light and away from strong light. If we stain the plant with iodine we can plainly see a pair of little whips arising from the clear portion at the forward end; it is by the lashing of these that the plant is enabled to swim. In the mud of our pond we may find a little colony of plants which might forgivably be mistaken for a collection of the individuals we have just studied. Each member of the colony is very much smaller than _Chlamydomonas_ to be sure, but each one has the outer membrane, the brownish eye spot and the pair of little whips. On the other hand the chlorophyll fills the whole of each cell and is not arranged in the form of a cup. Sixteen cells form a colony, and the whole mass is a flat plate; the little whips move in unison and the whole colony revolves after the manner of a wheel. Another little colony we may encounter also, consists likewise of sixteen cells very like the ones we have described, but somewhat wedge-shaped instead of oval. A jelly-like mantle encloses the colony and, in outline, it is spherical, so that when the little whips, which project through the mantle, lash the water the whole colony revolves. The most remarkable of these colonies of cells is known as _Volvox Globator_, it may be recognised by its perfectly spherical shape and its characteristic movements in water. _Volvox_ is about 1/25 inch in diameter, and although to the uninitiated it appears to be a single minute plant, in reality it is a colony of upwards of twenty thousand cells. The colony may be considered as being made up of thousands upon thousands of cells, very similar to those of _Chlamydomonas_, and each one arranged with its pair of little whips directed outwards.