HEADS OF PIKE, PICKEREL, AND HYBRIDS 



1. Head of adult pike. Extent of scale covering on operculum (gill-cover) indicated 



by white line. 



2. Head of adult pickerel, operculum fully scaled. 



3. Head of artificially produced hybrid. 



4. Head of supposed hybrid, captured in Cayuga Lake, N. Y. White line indicates 



extent to which scales cover operculum. 



Courtesy "American Journal of Heredity." 



