One of our seven wise men once said to me, "Have you observed that in the inorganic world things go by even numbers, and in the organic world by odd?" I immediately went down to the edge of a bushy and swampy meadow below our camp and brought him a four-petaled flower of galium, and a plant-stalk with four leaves in a whorl. In another locality I might have brought him dwarf cornel, or the houstonia, or wood-sorrel, or the evening-primrose. Yet even numbers are certainly more suggestive of mechanics than of life, while odd numbers seem to go more with the freedom and irregularity of growing things. One may make pretty positive assertions about non-living things. Crystals, so far as I know, are all even-sided, some are six and some eight-sided; snowflakes are of an infinite variety of pattern, but the number six rules them. In the world of living things we cannot be so sure of ourselves. Life introduces something indeterminate and incommensurable. It makes use of both odd and even, though undoubtedly odd numbers generally prevail. Leaves that are in lobes usually have three or five lobes. But the stems of the mints are four-square, and the cells of the honey bee are six-sided. We have five fingers and five toes, though only four limbs. Locomotion is mechanical and even numbers serve better than odd. Hence the six-legged insects. In the inorganic world things attain a stable equilibrium, but in the living world the equilibrium is never stable. Things are not stereotyped, hence the danger of dogmatizing about living things. Growing Nature will not be driven into a corner. Well may Emerson ask-- Why Nature loves the number five, And why the star form she repeats? The number five rules in all the largest floral families, as in the crowfoot family, the rose family (which embraces all our fruit trees), the geranium family, the flax family, the campanula family, the convolvulus family, the nightshade family. Then there is a large number of flowers the parts of which go in threes, one of the best known of which is the trillium. In animal life the starfish is the only form I recall based on the number five. IV. WHY AND HOW One may always expect in living nature variations and modifications. It is useless to ask why. Nature is silent when interrogated in this way. Ask her how, and you get some results. If we ask, for instance, why the sting of the honey bee is barbed, and those of the hornet and wasp and bumble-bee, and of other wild bees, are smooth like a needle, so that they can sting and sting again, and live to sting another day, while the honey bee stings once at the cost of its life; or why only one species of fish can fly; or why one kind of eel has a powerful electric battery; or why the porcupine has an armor of quills while his brother rodent the woodchuck has only fur and hair, and so on--we make no addition to our knowledge.