Published online by Cambridge University Press: 11 June 2012
Past studies of the relationships between different populations of Coregonus have demonstrated the great plasticity of form exhibited by this genus throughout the Palearctic region. In addition to standard morphological accounts, hybridization and rearing studies are important in attempting to assess the relationships between different races, and this paper describes some initial work which has been carried out in this direction. The development of eggs of the Loch Lomond powan, Coregonus clupeoides Lacépède, has been studied in the laboratory and shown to follow a definite pattern. The average incubation period at 6–9° C is 65 days though considerable variation in this time occurs. Eggs and sperm kept separate and without water still showed 50 per cent fertilization after 3 days but none after 6 days. Hybrids of two races of Coregonus, one living in Scotland the other in Wales, were produced by bringing together eggs and sperm which had been kept cool and dry during transport. The value of these experiments in relation to past and future research is discussed.