The diatoms often grow in long ribbon-like masses (_fig. 3_), and then partially separate, remaining joined together at the angles so as to form a zigzag chain as seen at _figure 4_. They have the power of moving through the water, changing their places like animals. A great variety of forms are found, both diatoms and desmids, many still undescribed, inviting the young microscopist to study and name them. _Figures_ 10 and 11 are different forms of a little animal, _Trichoda lynceus_. It undergoes a great many changes. In some of its stages, it looks so different from the figures here represented that you would never dream of its being the same creature. VIII.--THE VORTICELLAS. [Illustration: CARCHESIUM POLYPINUM.] The tree-vorticellas must ever stand first among all the varied and beautiful objects which the microscope reveals. A species common in New England and the Middle States is known scientifically by the name of _Carchesium Polypinum_. It is impossible to convey a true idea of its beauty from a dead black and white drawing. To be appreciated it must be seen in all its living glory--charming little animals resembling bell-shaped lilies on the ends of lovely transparent stems. How curious nature is in the microscopic world! Only think of a tree of living animals! The stems of the tree are jointed, and the little creatures can sway the branches about and even throw them into a spiral coil so as to bring themselves near the main stem. This gives them the appearance of being very polite toward each other; they bow and courtesy as if preparing for a grand quadrille, and they are decked out in gay colors, red, green, and yellow. The margins of the little cups are fringed with hairs, or _cilia_, which they can put in such rapid motion that it makes a current in the water and brings little particles to their mouths which they consume as food. They do not accept everything that comes in the current. They seem to know what they like as well as the higher animals, and act as if they were vexed with some of the particles, rejecting and sending them off with a rapid whirling motion. The largest of these fairy-like trees are visible to the naked eye, but it will be necessary for a novice in such matters to use a good strong lens to be able to find them readily. They are attached to plants growing in water. I have always been most successful in finding them among the water-milfoil (_Myriophillum_) several species of which grow in New England and the Middle States. Some of the species are found in deep water, others in shallow ponds. The Bladderworts (_Utricularia_) are also good plants to search among. They grow in similar places. On either of these plants we shall be sure to find a good many interesting creatures. If we fail to find the tree, we may secure other species of vorticella, all of which are very beautiful.