As I regard the discoveries made by Mr. Leakey in East Africa as of the highest importance for those of us who are inquiring into the antiquity of man, I should be sorry if in any way I have misrepresented his facts or his inferences. For my purpose his chief discovery is represented by the deepest burials in Gamble's cave. I am relieved to find that in attributing to these burials—the oldest found by him—an approximate contemporaneity with those of the Cromagnon people of Europe, I have not misled my readers. I did take extreme pains by a close study of his field reports and of all his published communications to ascertain not only his facts but also his inferences, and my failure must be due in part to the rapid evolution which Mr. Leakey's own knowledge has undergone, and must continue to undergo, in tho light of his additional discoveries. I am very glad he has been given this early opportunity of putting his present opinions, as well as corrections of my errors, before readers of NATURE.