One of the greatest interests of these lowly forms of life is their place in the evolution of the higher. We have left all that is familiar, the creatures with heads and limbs, far behind, on the surface as it were, and are groping among the foundations of the edifice of creation. It is difficult indeed to express how very far down we are without some description of the rest of the series. But this is impossible; I am asked to give means of understanding what a coral is, and should not be thanked for giving in reply a treatise on Zoology. Let us take two steps only of the process of evolution, and let these short lengths give an expression of the whole descent. Consider the vast interval of time and changes of structure involved in the evolution of man from his ape-like ancestor. How many thousands of years, what vast advances! How far above the purely animal is the lowest savage, and how far above that the best of civilised man! And yet even in the case of the brain, the development of which is man’s main advance, the man’s brain is but the further development of the ape’s[43], which has already gone the greater part of the way manwards from the condition found in ordinary animals. Now we and the apes together are derived from some fish-like ancestor. We all had gill bars fundamentally like those of a fish at one stage of our existences. It is a vast descent through the reptiles to the amphibia and then to the fishes[44]! And the fishes again are our second step illustrative of the vast changes involved. Fish are just fish to the ordinary man, and yet the fact is that the difference between man and ape is just nothing to that between the ordinary higher fish, the kinds that come in after the soup, and the sharks. The shark family have not yet attained the possession of true bone, for instance, and their brain development is almost rudimentary. But we are already in the dim beginnings of geological history, for sharks essentially like those we now know were living when almost the earliest of rocks were being laid down as mud in primeval oceans. These were times incredibly remote, when land animals were not in existence, when plants were represented only by seaweeds, the whole land a desert but for possibly some creeping films of vegetation adapted to life on damp soil ashore, times long ages before those strange reptiles Iguanodon, Diplodocus, the whale-like Ichthyosaurus, the giant ferns and lycopods of the coal measures, whose fossil remains remind us of nightmare worlds which have passed away, had ever come into being.