For those who are thinking of trying the experiment next time of being born twins, my advice is to choose parents who live near a library. Few parents would be able to afford to buy Mrs Burlingham's book, yet they could enjoy following the fortunes of the three pairs of identical twins the details of whose development are faithfully and clearly set out in charts. Such charts are expensive to print but they are indispensable here, and Imago Publishing Co. is to be congratulated on a beautiful as well as a valuable production.