Published online by Cambridge University Press: 14 August 2015
The Wolf-Rayet stars were the subject of a symposium held at the Joint Institute for Laboratory Astrophysics in Boulder, Colorado in June 1968. Here there was considerable discussion about whether one should talk about a class of objects called ‘Wolf-Rayet stars’ or whether it was more appropriate to talk about something called the ‘Wolf-Rayet phenomenon’ (Gebbie and Thomas, 1968). The point of view taken in this review is that it is more advantageous for obtaining an understanding of Wolf-Rayet objects to collate the available material under the broad category Wolf-Rayet phenomenon than to attempt to demonstrate that there is a homogeneous set of stars which can be called Wolf-Rayet stars and which occupy a significant stage in the evolution of stars, this stage being traversed routinely by all stars of a certain range of mass.