Vertebrate Photoreceptors *

Twenty-five years ago I landed in New Haven with a suit-case, a few dollars, and an urgent desire to study chemistry and biology of which I had already had the hors d'oeuvre, as it were. I was properly matriculated, with advanced standing, in the Sheffield Scientific School. Although I intended to major in chemistry, my chief concern that first week was how to earn "bread and butter," not to speak of meeting tuition and other charges less gastronomic in character. The only person I had ever heard of in New Haven was Professor Ross Harrison and I was told that he was an Embryologist. I finally found myself in his office, and with a timidity as great on that occasion as it is to-night, I presented to him the records of a few elementary observations which I had made in his subject-naturally seeking some credit. Credit was promised, with reservations! Just how it came to pass, I do not recall, but I was turned over to Professor Wesley R. Coe, then Division Officer, who, with the skill of a magician, showed me how I could get through Yale in one year instead of the expected two, provided, of course, that I would major in biology instead of chemistry. The case was quickly closed. Being from that moment on a presumptive biologist, I returned in due time to Professor Harrison, who undoubtedly did the greatest bit of academic gambling in his career by taking me on as laboratory assistant in the course in embryology for which I received the cherished sum of $5 per week. During that year as a senior in biology I was exposed to but one short course in zoology, and virtually became a botanist. To such an extent did I become a botanist that the following year, my first year of graduate work, I was made laboratory instructor in plant morphology, and became saturated with the odor of the bryophytes and the cryptogams. I