Page:The advancement of science by experimental research - the Harveian oration, delivered at the Royal College of Physicians, June 27th, 1883 (IA b24869958).pdf/40

 Darwin says, "I believe that animals are descended from at most four or five pro- genitors and plants from an equal or lesser number" (Origin of Species); but is num- ber anything with the Creator, or does He descend to our standard?

The development of higher animals is a gradual process and by successive stages; but, the presence of branchial fissures in the embryonic neck does not necessarily shew, that the animal is at that stage a fish; neither does the imperfect septum in the heart of the mammal during em- bryonic life show, that at that time it was a reptile. These gradations are doubtless the steps by which the end can be best attained; just as in the formation of a sheet of glass, the workman takes a por- tion of molten glass, but he does not roll it into a plate as one might suppose; on the contrary, he blows it into a sphere; then by gentle pressure, whilst he rotates the globe of glass, he moulds it into that which is well known as a glass shade; then, whilst still revolving, he cuts off the upper part and leaves a cylinder of glass;