_Lesson III._ The problem of this lesson has already been stated. The questions at the beginning of the lesson serve to help the child to interpret what he has observed, or what has been illustrated to him. The scene of this lesson need not be definitely located in space, for this book is a generalized account of progress, not a description of a particular locality. Should the teacher need assistance in getting a more adequate notion of a river valley, she will do well to read the following references, as well as the chapters on river valleys in any good textbook on geography or physiography. References: N. S. Shaler, _First Book in Geology_, pp. 1-4; Frye, _Brooks and Brook Basins. Aspects of the Earth_, chapter on "River Valleys." Winchell, _Walks and Talks in a Geological Field_. Rollin D. Salisbury and Wallace W. Atwood, _The Geography of the Devil's Lake Region, Wisconsin_, pp. 36-58. [NOTE. This pamphlet may be obtained by writing to Professor E. A. Birge, State University, Madison, Wis., and enclosing thirty cents. It is Bulletin No. 5, Educational Series No. 1.] R. S. Tarr, _Elementary Physical Geography_, pp. 262-82. _Lesson IV._ This lesson serves merely to bring out the striking contrasts that the geographical features mentioned in the last lesson present. The child can readily see why it was necessary for Sharptooth to swing from branch to branch instead of walking on the ground. _Lesson V._ Although the father was always more or less attached to the primitive group, it was the mother and child that constituted the original family. Not until the development of the patriarchal system in the pastoral stage of culture was the relation of the father recognized as of as great importance as that of the mother. The data from which the part of the story that deals with the way in which Sharptooth carried her baby was constructed was derived from the practices of contemporary tribes in the lowest stages of culture. It is a well-known fact that all young infants during the first few hours after birth possess the power to grasp and to hang suspended by the hands for several minutes. References: Loria, _Economic Foundations of Society_, p. 87. Thwing, _The Primitive Family_. C. N. Starcke, _Primitive Family in its Origin and Development_. G. L. Gomme, "The Primitive Human Horde," _Journal of the Anthropological Institute_, Vol. XVII., pp. 118-33; "The Evolution of the Family," _Popular Science Monthly_, Vol. XI., p. 257. Ch. Letourneau, _The Evolution of Marriage and the Family_.