This simple, first-published article by Mario Montessori was written in Kodaikanal, India, and reveals a great Montessori truth that has never been so explicit: There are developmental stages for practical life that cross over into nature study and living experiences. Although more abstract, the second plane has a strong practical life component that connects the six- to twelve-year-old to the real natural world. This emphasis on the second plane makes an even stronger, more unified connection between the developmental continuum that is completely embedded in the natural world before and after elementary. [This article is a synopsis of a lecture on the Kodaikanal Advanced Course of 1943-44, in Kodaikanal, India.]