To state the pedigree of man according to the Darwinian theory, we must begin with an aquatic animal as the early progenitor of all the vertebrata. This animal existing, it is assumed, "in the dim obscurity of the past," was provided with branchiæ or gills, or organs for respiration in water, with the two sexes united in the same individual, but with the most important organs of the body, such as the brain and heart, imperfectly or not at all developed. From this fish-like animal, or from some of its fish descendants, there was developed an amphibious creature, with the sexes distinct. Rising from the amphibians, through a long line of diversified forms, we come to an ancient marsupial animal, an order in which the young are born in a very incomplete state of development, and carried by the mother, while sucking, in a ventral pouch.[27] From the marsupials came the quadrumana[28] and all the higher mammals.[29] Among these mammals there was, it is supposed, a hairy, tailed quadruped, probably arboreal in its habits, from which man is descended. It was an inhabitant of the Old World. It branched into the lemuridæ, a group of four-handed animals, distinct from the monkeys, and resembling the insectivorous quadrupeds in some of their characters and habits;[30] and from these came the simiadæ, of which there were two great stems--the New World and Old World monkeys. "From the latter, at a remote period, man, the wonder and glory of the universe, proceeded."[31] The reader must now, in order to do justice to this theory, imagine a lapse of time, from the period of the existence of the aquatic progenitor of all the vertebrata, to be counted by millions of years, or by any figures that will represent to the mind the most conceivable distance between a past and a present epoch. Through this enormous stretch of centuries, in order to give scope to the operation of the laws of natural and sexual selection, we must suppose the struggle for existence to be going on among the individuals of the same species, and among different species inhabiting the same country, and the sexual selection among the individuals of the same species to be perpetually transmitting to offspring the improved and more developed organs and powers induced by natural selection; so that in the countless sequence of generations there are evolved animals that are so widely different from their remote progenitors that in classifying them we find them to be new species, endowed with a power of reproducing their own type, and similarly capable, it would seem, of still further development into even higher types in the long-distant future.