The cell was the first invention of the animal kingdom, and all higher animals are and must be cellular in structure. Our tissues were formed ages on ages ago; they have all persisted. Most of our organs are as old as worms. All these are very old, older than the mountains.
One of my friends, reading the title of these lectures [The Whence and Whither of Man] said: "Of man's origin you know nothing, of his future you know less."
Indeed, while Nature is wonderfully inventive of new structures, her conservatism in holding on to old ones is still more remarkable. In the ascending line of development she tries an experiment once exceedingly thorough, and then the question is solved for all time. For she always takes time enough to try the experiment exhaustively. It took ages to find how to build a spinal column or brain, but when the experiment was finished she had reason to be, and was, satisfied.
