We shall be better able to understand that process by studying how the seeds of different trees select from the common environments different materials, and absorb and assimilate different quantities of elements. Suppose two seeds, one of an oak and the other of a chestnut, are planted in a pot. The power of growth in both the seeds is of the same nature. The environments, earth, water, heat and light are the same. But still there is some peculiarity in each of the seeds, which will absorb from the common environments different quantities of elements and other properties which are fit to help the growth of the peculiar nature and form of the fruit, flower, leaves of each tree. Suppose the chestnut is a horse-chestnut. If, under different conditions, the peculiar nature of the horse-chestnut changes into that of a sweet chestnut, then, along with the changes in the seed, the whole nature of the tree, leaves, fruits will also be changed. It will no more attract, absorb or assimilate those substances and qualities of the environments which it did when it was a horse-chestnut. Similarly, through the law of "natural selection" the newly moulded thought-body of the dying person will choose and attract such parts from the common environments as are helpful to its proper expression or manifestation. Parents are nothing but the principal parts of the environment of the re-incarnating individual. The newly moulded inner nature or subtle body of the individual will by the law of "natural selection" involuntarily choose, or be unconsciously drawn to, as it were, its suitable parents and will be born of them. As, for instance, if I have a strong desire to become an artist, and if after a life-long struggle I do not succeed in being the greatest, after the death of the body I will be born of such parents and with such environments as will help me to become the best artist. The whole process is expressed in Eastern philosophy by the doctrine of the Reincarnation of the individual soul. Although this doctrine is commonly rejected in the West, it is unreservedly accepted by the vast majority of mankind of the present day, as it was in past centuries. The scientific explanation of this theory we find nowhere except in the writings of the Hindus; still we know that from very ancient times it was believed by the philosophers, sages and prophets of different countries. The ancient civilization of Egypt was built upon a crude form of the doctrine of Reincarnation. Herodotus says: "The Egyptians propounded the theory that the human soul is imperishable, and that where the body of any one dies it enters into some other creature that may be ready to receive it." Pythagoras and his disciples spread it through Greece and Italy. Pythagoras says: "All has soul; all is soul wandering in the organic world, and obeying eternal will or law." In Dryden's Ovid we read:--