With over 70 species still populating the world's oceans after approximately 500 million years, hagfishes are essential benthic organisms that play a vital role in understanding the evolutionary origins of vertebrate life and the maintenance of the oceanic ecosystem. Hagfish Biology is a long overdue book for communicating and furthering study on these unique animals. It provides an avenue of synergy among scientists interested in hagfish physiology, molecular and evolutionary biology, morphology, and protection. New high throughput sequencing technologies, advanced microscopy techniques, descriptions of hagfish embryology, and developments of techniques to understand ancient evolutionary relationships have led to a resurgence of interest in the hagfish as a key species in understanding the evolution of vertebrates. Inspired by these new research perspectives, this book compiles scientific information on hagfishes that is of interest to a range of fields such as ecology and evolution, comparative physiology, and conservation biology. A much-needed contribution, Hagfish Biology builds on previous knowledge while encouraging further expansion of scientific interest and learning about this fascinating yet understudied key evolutionary species. It introduces you to developing areas of research and provides beginning points for a larger conversation on hagfishes.