Modern thought since the publication of the "Origin of Species," has been more and more forced into the recognition of ethics, (together with all other forms of human conduct) as the result of a process of natural growth. The factors out of which this growth arose are lost in the obscurities of our ignorance, and many of the processes upon which it has depended also surpass existing human powers of explanation. Science has to take for granted the unexplained existence of organisms. For her purposes she is obliged to begin by assuming certain primitive organisms of some simple structure and functions. She is also obliged to admit, although she does not understand, the facts of reproduction and of heredity. Nor can she refuse to acknowledge a place in the history of development, along with the factors of chemistry and of physics, to a subjective factor called feeling, consciousness, mind, or however else it may be best expressed. All these unexplainable but fundamental verities of existence she has to assume. It is because these are unexplained that science falls short of becoming a philosophy. But within the range of their operation science can tell us much, and the Darwinian doctrines have displayed before our eyes the wonderful histories of change and growth through the preceding cycles of the world's existence. Little doubt now remains in the minds of thoughtful men as to the truth of biological development. The theory rests upon such a wide induction of facts extending over so many branches of science and over such remote periods of time, and withal as by a stroke of magic it has so arranged all sorts of odd incomprehensible facts into definite places in a well ordered organic history, that the mind can no longer withhold its subjection to so imperial and cogent a scientific conception. Although the philosophical laws of biological development are as we have seen beyond our reach, and although our theory of the accidental origin of variations is rather lame, still there is much that can be expressed in the formal statements called the Laws of Biological Development, which throws light upon those processes of change and growth that have led up from simple organic forms to the highest manifestation of life in the human race. Mr. Spencer defines life as "the continuous adjustment of inner relations to outer relations." This Mr. Spencer regards not merely as a definition but as a law. Its philosophical justification is sought in vain, but it may be accepted as a correct scientific statement--not only of the non-conscious adaptations of organisms to changes of the environment, (such as the thickening of the fur to resist arctic cold, or protective change of colour to imitate physical surroundings,) but also of the conscious adaptations by which higher animals perform particular actions or undergo changes of habit.