Notes from Donald Costello's lecture. Trinkaus continues from the previous two pages with his series of diagrams on the development of the barnacle embryo, including information on the cell lineageLecturer: D. P. Costello, Lecture "The Embryology of Crustacea" (Information taken from the 1939 Embryology Course Book)Page 50 of 72 from the second notebook of lecture and laboratory notes that John P. Trinkaus took during his time as a student in the Marine Biological Laboratory Embryology Course in 1939 in Woods Hole, MA