Nevertheless, taking the world round as it stands, we must believe that the distinction of seasons grew up, both for plants and animals, and for man or his ancestors, during this age of relatively unmarked summers and winters. For the tropics more than anywhere else preserve for us to-day the general features and aspect of this earlier time; they have never had the continuity of their stream of life rudely interrupted by the enormous changes of the Glacial epoch. Yet, even in the tropics, things, as we saw, have seasons. There are annuals and perennials there, as elsewhere. Each kind has its month for sprouting, for flowering, for fruiting, for shedding its seed; and men in the tropics, some of them long isolated in oceanic islands, or in great insulated regions like Australia or New Guinea, from the rest of their kind in the temperate regions, nevertheless know and observe the year, and perform all their functions, agricultural or religious, by yearly cycles. For example, there is among them all an annual feast for the dead, and widows mourn their husbands for one year from their burial. Observation of the year, therefore, both automatically by organisms at large and consciously by man, antedates and is independent of observation of the existence of summer or winter. I do not think, however, that man would have noted the merely astronomical year--the year of the sun's position--at least till a relatively late stage in culture, if he had not first noticed the organic year--the regular recurrence of plant and animal seasons. So many yams--that is to say, so many yam harvests--in other words, so many years, is a common savage way of reckoning times and ages. But they call it "yams," not summers or winters. And when I say yams, I give that merely as a single instance, for elsewhere the "seedtime and harvest" are reckoned indifferently in maize or millet, rice or barley, according to the agriculture of the particular people. Even hunting races know that at certain times of year certain foods abound; and this is true of equatorial savages and equatorial plants or animals, as well as of others.