In science, moreover, the work of the individual is so bound up with that of his scientific predecessors and contemporaries that it appears almost as an impersonal product of his generation.

From the story "The Progress of Science" in The Scientific Monthly edited by J. McKeen Cattell (June 1921), Vol. XII, No. 6. The story says that the comments were made at the annual meeting of the National Academy of Sciences at the National Museum in Washington on April 25, 26, and 27. Einstein's comments appear on p. 579, though the story may be paraphrasing rather than directly quoting since it says "In reply Professor Einstein in substance said" the quote above.