Let the reader imagine a tree with slender, gracefully curved, and tapering branches thickly studded over with delicate flower-bells in place of leaves. Let him suppose the bells to be shaped somewhat between those of the fox-glove and convolvolus, and the stem, branches, bells, and all, made of the purest crystal. Let him further conceive every component part of this singular structure to be tremulous with life-like motion, and he will have as correct an idea as words can give of the complex form of this minute inhabitant of the deep. Moreover, while gazing at it through the microscope, the observer is startled by the sudden collapse of the entire structure. The lovely tree has shrunk together into a dense ball, in which the branching stem lies completely hidden among the flower-bells--themselves closed up into little spherules, so closely packed together that the entire mass resembles a piece of herring-roe. This contraction is so instantaneous that the mode in which it is accomplished cannot be observed until the tree is again extended. As the re-extension takes place very slowly, we are enabled to observe that each branchlet has been coiled in a spiral form, like the thread of the simple Vorticella previously described; and also that the main stem, above the lowest branch, was coiled up in the same way, but not so closely, and that the part below the lowest branch had, curiously enough, remained straight. Sometimes, in large and numerously branched specimens, one or two of the lowest members do not contract at the same time with the rest, but do so immediately afterwards, as if they had been startled by the shrinking movements of their neighbours. Sometimes these lowest branches will contract alone, while all the others remain fully extended,--a fact that would almost seem to indicate that they possessed an independent life of their own. In the accompanying engraving I have attempted faithfully to portray one of these wonderful creatures. Fig. 1 represents it fully extended, while Fig. 2 indicates its collapsed form. There is another curious circumstance which I have fortunately observed in connection with this Vorticella, a description of which will perhaps be interesting to the reader. I allude to the casting off of what may be called the fruit of the tree. When this event takes place, the buds (or fruit) dart about with such rapidity, that it is almost impossible to keep them in the field of view for the briefest space of time. A represents the enchanted fruit hanging on the tree; B shows it as it swims about. [Illustration: Fig. 1. and Fig. 2.]