A and B were born by Caesarean section, somewhat prematurely, weighing 4.3 pounds and 5.3 pounds, respectively. Notwithstanding their premature birth, in six months A was able to rise spontaneously to a sitting posture in her mother's lap, and very soon thereafter B did likewise. At 11 months both had begun to walk, and to talk in sentences. At the age of 3 years they began the study of French, and in less than a year from that time they were reading elementary English, French, and Esperanto. At the age of 4 they could distinguish parts of speech. They entered the third grade in school at the age of 6 years, and at the time of report they had achieved the seventh grade and were engaged in junior high school work at the age of 9 years. They are not prigs: they are attractive, animated, sociable children, with a bubbling sense of humor. They are popular with their playmates. They can take charge of a gymnasium class in which most of the members are two to four years their seniors, and preserve excellent attention and discipline. They speak mature but not pedantic English, and they speak French with the fluency of a native. They have read the _Book of Knowledge_ in its entirety in French; and a year ago embarked on Russian. They play duets on the piano, but not with rare distinction. They swim; they ride horseback; they write jingles; and they read by the hour. Their school work does not tax them; they do not worry about it; and they are far from fastidious in regard to the form of their written work. A complete family chart of the twin sisters, A and B, would show evidence of superior endowment in the immediate ancestry on both the maternal sides. Scientific and linguistic ability of high order and physical energy are some of the traits which are found in the two immediate generations. The trait of twinning likewise has a hereditary basis in this instance, for the mother also bore two boys, twins who died in infancy. Measurements of physique show A and B to be slightly smaller than children of their age in good private schools, but very well nourished. The children have no living brothers or sisters. _Elizabeth, reported by Hirt_. Elizabeth was reported from the public schools of Erie, Pennsylvania, in 1922, by Hirt (13). She was born January 16, 1914, and was tested June 14, 1921, aged 7 years 5 months. Her Mental Age was found to be 14 years, 0 months, yielding an IQ of 189 (S-B).