A doctor who specializes in the field of multiple births (twins, triplets, etc.), gives a popular-scientific account of the physiological-psychological inquiries and problems that arise concerning them. I found it very interesting. Basic biological facts are given; sociological importance; the hazards; the causes; the contribution double experimentation has made to science, to psychology, to child training. On the lighter side anecdotes liven the record. There's material about oddities such as the Siamese twins -- quintuplets -- a good deal on the Dionnes. Very specialized but good of its kind.