5. Other points of resemblance exist between plants and animals. If they are not generally remarked, it is because the authors of the classics of natural history do not direct the attention of the reader to these facts. We are about to supplement their silence, and to bring the analogies between the two natural kingdoms into view. Firstly, there exists in both a common and equally astonishing fecundity. Among plants, as among animals, one individual can give birth to thousands of individuals like himself. Vegetables are even more fertile than the superior animals. Trees produce every year, and sometimes for a century. Mammiferous animals, birds, and reptiles produce infinitely less than trees; their pregnancy is less frequent, and takes place during a certain period in the life of the animal only. The elm produces every year more than 300,000 seeds, and this may continue for a hundred years. Fish and insects approach most nearly to trees in fecundity. A tench spawns 10,000 eggs yearly, a carp 20,000. Among insects, a female bee produces from 40,000 to 50,000 eggs. To these animals we may compare, among vegetables, the poppy, the fern, the mustard plant, which produce incalculable quantities of seeds. We must not forget, besides, that vegetables multiply themselves in many ways, whereas each animal possesses but one mode of reproduction. What we wish to establish, what is evident, is that among both animals and plants fecundity is equal, and equally prodigious. From the point of view of this analogy, we may also quote the size of the species, which is extremely variable in both kingdoms, because both produce at the same time giant species and dwarf species. Among animals, there are some of monstrous size, such as the whale, the cachalot, and the elephant, such as the gigantic reptiles of the ancient world, the ichthyosaurus, which was longer than the whale, the megalosaurus and the iguanadon, which were as large as the elephant. To these colossi of the animal kingdom, we may oppose the colossi of the vegetable kingdom; the monstrous baobab gourd, which covers hundreds of square yards with its shade, the elm, whose trunk may grow to the size of a whale's girth, the _Eucalyptus globulus_, an Australian tree which is being acclimatized in Algeria and in the south of France, the _Sequioœa gigantea_, the giant of Californian forests. If the two kingdoms of nature have their colossi, they have also their dwarfs, and their infinitely little. There are cryptogamic vegetables which are only to be seen with the microscope, and there are animalculæ equally invisible to the naked eye. If the animal kingdom can show, in its scale of size, the whale, and the microscopic _acarus_, the vegetable kingdom possesses a similar decreasing scale from the baobab to the lichens.