Under the head of Attention comes such games as Hide and Seek, because of the alternate stress and relaxation, and Froebel noted before Darwin did the pleasure of the baby in Bo-peep. Groos also brings curiosity under this heading, and we have seen that Froebel deals fully with such play as the outcome of the instinct of investigation, or the instinct for self-teaching. Froebel would certainly not draw the line where Groos does, when he says “the true characteristics of play are in inverse ratio to the intensity of the desire for knowledge,” and if this rule were strictly adhered to, a good deal of what Groos does call play might have to come out. The plays which fall under the head of Reason have two bearings, says Groos, first causality, and second inherence. There are various references to the “joy of being a cause” from the child “whose capacity for speech is as yet undeveloped,” but who draws away the support and as the cube falls “turns to his mother in joyous triumph,” up to the pride of Keilhau boys, who “might not have accomplished their fortresses without the sapper,” but “who believed that if cast on a desert island, each could build a hut of his own.” Froebel also brings in intellectual games such as draughts, and he notes how children will invent their own words and their own alphabets in play. Of the making and solving of riddles I think Froebel never speaks. As to what Groos says of Experimentation with the feelings, the parallels in Froebel are surprise plays such as Hide and Seek, adventure and hunting games where there may be play with fear, and the legends and stories. Under the Impulse of the Second or Socionomic order, come the Fighting Plays, Love Play, Imitative Play, and Social Play. Of Love Play, Froebel has none, but the hunting and fighting were allowed abundant scope at Keilhau. Of Imitative Play there is much that can be cited from the playful imitation of simple movements and sounds in the Mother Songs and the Kindergarten Games, to the “classic dramas” of the Keilhau boys. Plastic and constructive play, too, goes from the simplest sand play, through the Kindergarten handwork, not only up to the fortress making, but also to the “boxes with locks and hinges, so neatly finished, veneered, and polished that many a trained cabinet-maker’s apprentice could have done no better,” which were made at Keilhau.