Aversion is taught as easily as terror, when the object of it is neutral and not especially attractive to an unprejudiced taste. I can testify in my own person to the somewhat rapidly-acquired and long-retained fancies concerning the clean and unclean, upon which Jews and Mussulmans lay such curious stress. It was the result of my happening to spend a year in the East, at an age when the brain is very receptive of new ideas, and when I happened to be much impressed by the nobler aspects of Mussulman civilisation, especially, I may say, with the manly conformity of their every-day practice to their creed, which contrasts sharply with what we see among most Europeans, who profess extreme unworldliness and humiliation on one day of the week, and act in a worldly and masterful manner during the remaining six. Although many years have passed since that time, I still find the old feelings in existence--for instance, that of looking on the left hand as unclean. It is difficult to an untravelled Englishman, who has not had an opportunity of throwing himself into the spirit of the East, to credit the disgust and detestation that numerous every-day acts, which appear perfectly harmless to his countrymen, excite in many Orientals. To conclude, the power of nurture is very great in implanting sentiments of a religious nature, of terror and of aversion, and in giving a fallacious sense of their being natural instincts. But it will be observed that the circumstances from which these influences proceed, affect large classes simultaneously, forming a kind of atmosphere in which every member of them passes his life. They produce the cast of mind that distinguishes an Englishman from a foreigner, and one class of Englishman from another, but they have little influence in creating the differences that exist between individuals of the same class. HISTORY OF TWINS.