Lecture XII

But these stages are not final; evolution gradually progresses. Even today the solar plexus is an active agent in certain animals which have not developed a spinal cord. All invertebrate animals are single forms from left behind stages of what was laid down earlier. It was only on the Earth that man cast out from himself the vertebrate animals. In earlier times his organism was still somewhat similar to that of the crab at the present day. Man has progressed beyond that earlier stage whereas the crab has remained stationary. It is an astonishing fact that the whole inner formation of the crab has a certain similarity to the human brain. There is actually a similarity between the internal formation of the crab and the human brain. Like the human brain the crab too is enclosed in a hard shell. After man had developed a spine and had metamorphosed the upper vertebrae, he cast off the hard shell. The crab has not developed further. It has adapted itself to its environment by means of a hard shell that it had to have and which serves the same purpose as does the protective covering of the whole body in man.