GYRODACTYLUS EUCALIAE N. SP. (TREMATODA: MONOGENEA) FROM THE BROOK STICKLEBACK, EUCALIA INCONSTANS*

A new species of Gyrodactylus was observed on the skin, gills, and fins of the brook stickleback from the English Coulee, Grand Forks, North Dakota during the summers of 1953-1955. Host-specificity is usually striking in the monogenetic trematodes and since this parasite was not observed on any other species of fish from this body of water or the nearby Turtle River, it was studied in detail and is here described as a new species, G. eucaliae. Ether chloretone, chloroform, or menthol at 0.5%, or urethane or nembutal at 0.1 to 0.5%, in aqueous solution, were used in recovering the intact worms from the host. The best solutions proved to be 0.5 % urethane and 0.5 % nembutal. One is cautioned concerning the carcinogenic properties of urethane (Wood, 1956). A convenient field method of collecting the parasites in large numbers consisted of placing the fish in a bottle of 0.5 % nembutal or urethane; the parasites left the host within 3 to 5 minutes and the hosts were discarded; the fish survived about 5 min-utes. Parasites so obtained remained suitable for study for several hours. They were concentrated by sedimentation and fixed in hot 5 % glycerine-5 % formali