This transcription of notes made by Charles Darwin during the voyage of H. M. S. Beagle records his observations of the animals and plants that he encountered, and provides a valuable insight into the intellectual development of one of our most influential scientists. Darwin drew on many of these notes for his well known Journal of Researches (1839), but the majority of them have remained unpublished. This volume provides numerous examples of his unimpeachable accuracy in describing the wide range of animals seen in the course of his travels, and of his closely analytical approach towards every one of his observations. Only at the very end of the voyage were his first doubts about the immutability of species expressed consciously, but here are to be found the initial seeds of his theory of evolution, and of the fields of behavioural and ecological study of which he was one of the founding fathers.