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A Thesis Presented to The Faculty of Graduate Studies of The University of Guelph by CHARLES D. BERNHOLZ In partial fulfilment of requirements for the degree of Master of Arts, September, 1973.

© Charles D. Bernholz, 1973


Critical flicker frequency (CFF) in a free-swimming harp seal (Pagophilus groenlandicus) was investigated using behavioral techniques. The resulting CFF versus intensity contour indicates a definite rod-cone break, confirming a duplex photoreceptor population whose presence had not been observed in previous morphological reports.