The family, Centrarchidae, is indigenous only to North America, and consists of 30 fish species (Blair et al., '57). Several have been studied extensively by fishery biologists, and the systematics have been carefully considered by Hubbs and Bailey. However, the family has received only scant attention from cytologists.The earliest reference to centrarchid chromosomes was by Bright ('40), who made chroirnosome counts during an investigation of spermiogenesis. He studied testes preparations of Helioperca macrochira (= Lcpomis macrochirus), Apomotis cyanellus (== Lepomis cyanellus), and their hybrid, and reported a diploid number of "circa 4 2 for each. He did not indicate his stain or method of' slide preparation.Baker ('56) carried out a chromosome study of five species of centrarchids using aceto-carmine squash preparations of testes. He reported a diploid number 01 48 for Lepomis macrochirus, and "circa" 48 for Ambloplites rupestris, Pomoxis annularis, Centrarchus nzacropterus, and Micropterus salmoides. Baker described rodshaped, J-shaped ( acrocentric) , V-shaped (metacentric), and spherical chromosomes, but he apparently misinterpreted chance variations in shape and chromatid separation.The present study reconsiders the karyotypes of these species, hitherto inadequately handled, and extends cytological attention to 15 additional centrarchid species. MATERIALS AND METHODS CollectionsSpecimens were collected in North Carolina, Tennessee, Kentucky, and West Virginia with seines, rod and reel, rotenone, and creosol. Lepomis microlophus, Amblo-J. MORPH., 115: 401-418.

A karyotypic study was conducted with Salmo salar from West Grand Lake in northern Maine and from Craig Brook National Fish Hatchery originally from Lake Memphremagog), Orland, Maine. Specimens from the latter population were culled abnormal females with the exception of a single normal male and female. The culls gave a mode of 56, whereas all others gave a mode of 57. The difference, as well as general variation, tended to follow a Robertsonian pattern. In addition, a large submetacentric chromosome with a constriction in the long arm was found more commonly in karyotypes from the culled fish. The variation may be a result of the mixing of isolated populations in which divergent karyotypic evolution has occurred.

Electrophoretic examination of 56 wild Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) from the Stewiacke River, Nova Scotia, revealed one individual believed to be a hybrid between these two species. The possibility of loss of the genetic integrity of each species is considered. A long history of sympatry between Atlantic salmon and brown trout in Europe may have prevented the formation of hybrid swarms as occurred in western North America following introduction of nonindigenous Salmo.Key words: electrophoresis, introgression, enzymes, genetic interaction

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The chromosomes of sea‐run Atlantic Salmon from three North American rivers were studied with cell culture preparations. Extensive data from Machias River (Maine) specimens showed a sharp mode of 54 chromosomes. Modes of 55 for the Narraguagus River (Maine) and 56 for the Miramichi River (New Brunswick) represented much smaller percentages of their counts. A relatively constant arm number of 72 indicates a Robertsonian pattern of polymorphism.