Presently the sponge of time may wipe out the common ancestry at the root of the lateral tree, and nothing be left but some of its ascending and some of its descending branches,—all suited to their environment and so continuing to live and flourish, each in its own way; but so apparently different, that relationship between them is a matter of inference, and is sometimes difficult to believe in. The example of the caterpillar and butterfly, however, of the tadpole and the frog, etc., can be used to remove incredulity at extraordinary and instructive transmutations—transmutations which in the individual represent rapidly some analogous movements of racial development in the history of the distant past. The degradation of certain free-swimming animals, such as ascidians, which in old age become rooted or sessile like plants, can be pointed to as typical, and, indeed, a true representation of what has gone on in a race also, during long periods of time. The rapid passage of the embryo through its ancestral chain of development should be known, at any rate to the teacher; and in general the greater the teacher’s acquaintance with natural history, the more living and interesting will be the series of lessons that can occasionally be given on this part of the clause. The popular misconception concerning the biological origin of man, that he is descended from monkeys like those of the present day, is a trivial garbling of the truth. The elevated and the degraded branches of a family can both trace their descent from a parent stock; and though the distant common ancestor may now be lost in obscurity, there is certainly in this sense a blood relationship between the quadrumana and the bimana: a relationship which is recognised and is practically useful in the investigations of experimental pathology. LOWER FORMS OF ANIMAL LIFE.—The existence of single cells and other low microscopic forms (like amœbæ), and the analysis or dissection of a more complex structure (say rhubarb) into the cells of which it is in a sense composed, together with some indication of the vital processes occurring in similar but isolated cells (such as yeast or protococcus) which lead us to consider them as possessing life—of a form so fundamental that there is in some cases no clear discrimination between animal and vegetable—may be spoken of and exhibited in the microscope. From a not very different-looking minute germinal vesicle, or nucleus of a cell, the chick is developed.