According to biological ethics, the fundamental obligations of all living things are the same, even though the modes of discharging them may be various. Every individual must lead an efficient personal life by procuring food, but animals differ very much in their alimentary apparatus; among other things they must respire, but some are so simply organized that they do not need elaborate organs like the tufted gills of a crustacean or the lungs of higher vertebrates. Every individual of whatever grade must also provide in some way for the maintenance of the species, but some, like a conger eel, produce enormous numbers of eggs which are left uncared for, while others, like birds, bring forth only a few young, which receive constant attention and protection until they are able to shift for themselves. Nature has no place for even a human community unless individual and racial interests are conserved, so that the greatest duties are definitely formulated--all else is secondary and less essential. Selfish action on the part of every unit is obligatory, but it must always be antecedent to endeavor in the wider interests of the race if the unit is a solitary individual; if it is a member of an association of any grade, then it must serve its fellows in some way. Egoism and altruism are natural essential guides to conduct; neither can safely exclude the other, and their antithesis sets a problem for every organism, which is to work out the proper compromise that will be most satisfactory to nature. The Golden Rule is taught by biology because it is demonstrated empirically, and not because it has any _a priori_ value as an ideal ethical principle.