Shagwa Lake (previously called Long Lake) at Ely, Minnesota has been known to show a high incidence of fish infected with plerocercoids of Diphylobothrium latum over a period of many years. The last reported survey made of this lake (July 1937) appears to be that published by Essex (1938). We had the opportunity of obtaining figures on the present status of the infection of fish in Shagwa Lake in August 1950 when we collected plerocercoids in order to obtain adult tapeworms to be used for physiological studies.
Approximately one week elapsed after the fish were caught before they were dissected; during this time they were packed in ice. The muscle tissue was teased apart with utmost care in order to discover as many larvae as possible. In many instances soaking the shredded muscle in saline facilitated the recovery of plerocercoids which might otherwise have been overlooked.
The authors wish to thank Drs. Eloise B. Cram and M. S. Ferguson for aid in the dissection of the fish.