"It was evidently a case of love at first sight, for she swam about the newcomer caressingly, though he appeared evidently alarmed and averse to her overtures of affection. From that hour she forgot her old partner. Winter passed by, and the next spring the pintail seemed to have become a convert to her blandishments, for they nested and produced seven or eight young ones."[95] I am tempted to wait to consider the immense significance of such cases as these in the analogy they bear to our own sudden preferences in love. The question as to the moral conduct of this duck opens up suggestions of those cases of exceptional love-passions, which all our existing institutions, laws and penalties have never been able to crush. The desire for sexual variety is the ultimate cause of all sexual lapses and irrationalities. It is a mistake to think that this is a condition peculiar to mankind and the result of civilisation. If this were so it would be easier to deal with; but before these deeply-rooted instincts of sexual hunger we are often powerless. I know of no question that needs to be faced by women more than this one. I would like to say more about it. But already this first section of my book has exceeded its limits. I must, therefore, pass on, to draw attention to the fact, clearly proved by the case of this wild-duck's love, as well as by many other examples, that it is the females, who, exercising their right of selection much more than the males, introduce individual preference into their sexual relationships. The difficulty is that such preference, of profound biological importance, is often thwarted among civilised people by considerations of property and the accepted morality. From this standpoint permanent marriage may often fail to do justice to the sexual needs both of the individual and the wider needs of the race. Nature has no care for sex-morals as we understand them, any mode of sexual union is equally right so long as it serves the race-process. But men have set up a whole host of prohibitions and conventions--the "thou shalt nots" of society and religion. Which are we to follow? Which is the wheat and which the tares, that must be garnered or sifted from our loves?