"The ethical corollaries to Darwin's doctrine of the origin of species and to his theory of development through descent under the modifying influences of environment and natural selection have already passed these bounds of beneficence not only by demanding the mitigation of cruelty to slaves, but also by the abolition of slavery, and not only by inculcating the kind treatment of animals by individuals, but also by asserting the principle of animals' rights and the necessity of vindicating them by imposing judicial punishments for their violation."